Docstoc

Networking All-in-One For Dummies

Document Sample
Networking All-in-One For Dummies Powered By Docstoc
					                                ™
Making Everythin
                g Easier!                         4th Edition




        Networking           A L L- I N - O
                                            N E




91     BOOKS
       IN
• Networking Basics
• Building a Network
• Network Administration and Security
• TCP/IP and the Internet
• Wireless Networking
• Mobile Networking
• Windows Server® 2008 R2 Reference
• Using Other Windows Servers
• Managing Linux® Systems


Doug Lowe
           Get More and Do More at Dummies.com ®
                                                   Start with FREE Cheat Sheets
                                                   Cheat Sheets include
                                                      • Checklists
                                                      • Charts
                                                      • Common Instructions
                                                      • And Other Good Stuff!

              To access the Cheat Sheet created specifically for this book, go to
                           www.dummies.com/cheatsheet/networkingaio



Get Smart at Dummies.com
Dummies.com makes your life easier with 1,000s
of answers on everything from removing wallpaper
to using the latest version of Windows.

Check out our
   • Videos
   • Illustrated Articles
   • Step-by-Step Instructions

Plus, each month you can win valuable prizes by entering
our Dummies.com sweepstakes. *

Want a weekly dose of Dummies? Sign up for Newsletters on
  • Digital Photography
  • Microsoft Windows & Office
  • Personal Finance & Investing
  • Health & Wellness
  • Computing, iPods & Cell Phones
  • eBay
  • Internet
  • Food, Home & Garden


Find out “HOW” at Dummies.com
*Sweepstakes not currently available in all countries; visit Dummies.com for official rules.
Networking
  ALL-IN-ONE
    FOR

DUMmIES
                   ‰



          4TH EDITION
Networking
  ALL-IN-ONE
     FOR

DUMmIES
                    ‰



           4TH EDITION




  by Doug Lowe
Networking All-in-One For Dummies®, 4th Edition
Published by
Wiley Publishing, Inc.
111 River Street
Hoboken, NJ 07030-5774
www.wiley.com
Copyright © 2011 by Wiley Publishing, Inc., Indianapolis, Indiana
Published by Wiley Publishing, Inc., Indianapolis, Indiana
Published simultaneously in Canada
No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or
by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permit-
ted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written
permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the
Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 646-8600.
Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley
& Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://
www.wiley.com/go/permissions.
Trademarks: Wiley, the Wiley Publishing logo, For Dummies, the Dummies Man logo, A Reference for the
Rest of Us!, The Dummies Way, Dummies Daily, The Fun and Easy Way, Dummies.com, Making Everything
Easier, and related trade dress are trademarks or registered trademarks of John Wiley & Sons, Inc. and/
or its affiliates in the United States and other countries, and may not be used without written permission.
All other trademarks are the property of their respective owners. Wiley Publishing, Inc., is not associated
with any product or vendor mentioned in this book.

LIMIT OF LIABILITY/DISCLAIMER OF WARRANTY: THE PUBLISHER AND THE AUTHOR MAKE NO
REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF
THE CONTENTS OF THIS WORK AND SPECIFICALLY DISCLAIM ALL WARRANTIES, INCLUDING WITH-
OUT LIMITATION WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE. NO WARRANTY MAY BE
CREATED OR EXTENDED BY SALES OR PROMOTIONAL MATERIALS. THE ADVICE AND STRATEGIES
CONTAINED HEREIN MAY NOT BE SUITABLE FOR EVERY SITUATION. THIS WORK IS SOLD WITH THE
UNDERSTANDING THAT THE PUBLISHER IS NOT ENGAGED IN RENDERING LEGAL, ACCOUNTING, OR
OTHER PROFESSIONAL SERVICES. IF PROFESSIONAL ASSISTANCE IS REQUIRED, THE SERVICES OF
A COMPETENT PROFESSIONAL PERSON SHOULD BE SOUGHT. NEITHER THE PUBLISHER NOR THE
AUTHOR SHALL BE LIABLE FOR DAMAGES ARISING HEREFROM. THE FACT THAT AN ORGANIZA-
TION OR WEBSITE IS REFERRED TO IN THIS WORK AS A CITATION AND/OR A POTENTIAL SOURCE
OF FURTHER INFORMATION DOES NOT MEAN THAT THE AUTHOR OR THE PUBLISHER ENDORSES
THE INFORMATION THE ORGANIZATION OR WEBSITE MAY PROVIDE OR RECOMMENDATIONS IT
MAY MAKE. FURTHER, READERS SHOULD BE AWARE THAT INTERNET WEBSITES LISTED IN THIS
WORK MAY HAVE CHANGED OR DISAPPEARED BETWEEN WHEN THIS WORK WAS WRITTEN AND
WHEN IT IS READ.

For general information on our other products and services, please contact our Customer Care
Department within the U.S. at 877-762-2974, outside the U.S. at 317-572-3993, or fax 317-572-4002.
For technical support, please visit www.wiley.com/techsupport.
Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may
not be available in electronic books.
Library of Congress Control Number: 2010935591
ISBN: 978-0-470-62587-3
Manufactured in the United States of America
10 9 8 7 6 5 4 3 2 1
About the Author
    Doug Lowe has written a whole bunch of computer books, including more
    than 40 For Dummies books, among them Networking For Dummies, 9th
    Edition, Java All-in-One For Dummies, 3rd Edition, PowerPoint 2010 For
    Dummies, and Word 2010 All-in-One For Dummies. He lives in sunny Fresno,
    California, where the motto is “Fres-YES!,” (unfortunately, I’m not making that
    up). He’s one of those obsessive-compulsive decorating nuts who creates
    computer-controlled Halloween decorations that rival Disney’s Haunted
    Mansion.
Dedication
    To My Family.




Author’s Acknowledgments
    I’d like to thank everyone who was involved with the fourth edition of this
    book, especially the most excellent project editor Blair Pottenger, who put
    up with late submissions and who did a great job following through on all the
    little editorial details needed to put a book of this scope together on time.
    Thanks also to Dan DiNicolo, who gave the manuscript a thorough review to
    ensure the technical accuracy of every sentence, and in the process offered
    many excellent suggestions for improvements, and to copy editor Virginia
    Sanders, who whipped my prose into shape, crossing all the i’s and dotting
    all the t’s, or something like that. And, as always, thanks to all the behind-the-
    scenes people who chipped in with help I’m not even aware of.
Publisher’s Acknowledgments
We’re proud of this book; please send us your comments at http://dummies.custhelp.com.
For other comments, please contact our Customer Care Department within the U.S. at 877-762-2974,
outside the U.S. at 317-572-3993, or fax 317-572-4002.
Some of the people who helped bring this book to market include the following:

Acquisitions and Editorial                        Composition Services
Project Editor: Blair J. Pottenger                 Project Coordinator: Patrick Redmond
Acquisitions Editor: Amy Fandrei                   Layout and Graphics: Carl Byers,
Copy Editor: Virginia Sanders                         Samantha K. Cherolis, Ronald G. Terry

Technical Editor: Dan DiNicolo                     Proofreaders: Laura L. Bowman,
                                                      Jessica Kramer
Editorial Manager: Kevin Kirschner
                                                   Indexer: Broccoli Information Managment
Editorial Assistant: Amanda Graham
                                                   Special Help
Sr. Editorial Assistant: Cherie Case                  Annie Sullivan
Cartoons: Rich Tennant
   (www.the5thwave.com)


Publishing and Editorial for Technology Dummies
    Richard Swadley, Vice President and Executive Group Publisher
    Andy Cummings, Vice President and Publisher
     Mary Bednarek, Executive Acquisitions Director
    Mary C. Corder, Editorial Director
Publishing for Consumer Dummies
    Diane Graves Steele, Vice President and Publisher
Composition Services
    Debbie Stailey, Director of Composition Services
                  Contents at a Glance
Introduction ....................................................................... 1
Book I: Networking Basics .................................................. 7
Chapter 1: Understanding Networks ................................................................................................ 9
Chapter 2: Understanding Network Protocols and Standards ................................................... 21
Chapter 3: Understanding Network Hardware ............................................................................. 43
Chapter 4: Understanding Network Operating Systems.............................................................. 61

Book II: Building a Network.............................................. 75
Chapter 1: Planning a Network ....................................................................................................... 77
Chapter 2: Installing Network Hardware ....................................................................................... 95
Chapter 3: Setting Up a Network Server ...................................................................................... 111
Chapter 4: Configuring Windows Clients ..................................................................................... 121
Chapter 5: Macintosh Networking ................................................................................................ 135
Chapter 6: Configuring Other Network Features ........................................................................ 141
Chapter 7: Verifying Your Network Installation ......................................................................... 151
Chapter 8: Going Virtual ................................................................................................................ 157

Book III: Network Administration and Security ................. 169
Chapter 1: Help Wanted: Job Description for a Network Administrator ................................. 171
Chapter 2: Security 101 .................................................................................................................. 185
Chapter 3: Managing User Accounts ............................................................................................ 195
Chapter 4: Firewalls and Virus Protection .................................................................................. 203
Chapter 5: Extending Your Network with VPN Access .............................................................. 215
Chapter 6: Managing Network Software ...................................................................................... 221
Chapter 7: Solving Network Problems ......................................................................................... 233
Chapter 8: Network Performance Anxiety................................................................................... 249
Chapter 9: Backing Up Your Data ................................................................................................. 259
Chapter 10: Disaster Recovery and Business Continuity Planning .......................................... 271

Book IV: TCP/IP and the Internet ..................................... 279
Chapter 1: Introduction to TCP/IP and the Internet .................................................................. 281
Chapter 2: Understanding IP Addresses ...................................................................................... 289
Chapter 3: Using DHCP .................................................................................................................. 307
Chapter 4: Using DNS ..................................................................................................................... 321
Chapter 5: Using FTP ...................................................................................................................... 347
Chapter 6: TCP/IP Tools and Commands .................................................................................... 371
Book V: Wireless Networking .......................................... 397
Chapter 1: Setting Up a Wireless Network .................................................................................. 399
Chapter 2: Securing a Wireless Network ..................................................................................... 419
Chapter 3: Hotspotting .................................................................................................................. 431
Chapter 4: Troubleshooting a Wireless Network ....................................................................... 437
Chapter 5: Wireless Networking with Bluetooth ........................................................................ 443

Book VI: Mobile Networking............................................ 449
Chapter 1: Managing Mobile Devices ........................................................................................... 451
Chapter 2: Managing BlackBerry Devices ................................................................................... 455
Chapter 3: Managing iPhone Devices........................................................................................... 461
Chapter 4: Managing Android Devices ........................................................................................ 469
Chapter 5: Managing Netbooks ..................................................................................................... 473

Book VII: Windows Server 2008 Reference ....................... 477
Chapter 1: Installing and Configuring Windows Server 2008 R2............................................... 479
Chapter 2: Managing Windows Server 2008 ................................................................................ 493
Chapter 3: Dealing with Active Directory .................................................................................... 509
Chapter 4: Managing Windows User Accounts ........................................................................... 519
Chapter 5: Managing a File Server ................................................................................................ 539
Chapter 6: Using Group Policy ...................................................................................................... 553
Chapter 7: Troubleshooting .......................................................................................................... 563
Chapter 8: Windows Commands .................................................................................................. 575

Book VIII: Using Other Windows Servers .......................... 603
Chapter 1: Using Internet Information System (IIS) ................................................................... 605
Chapter 2: Managing Exchange Server 2010 ............................................................................... 615
Chapter 3: Using SQL Server 2008 ................................................................................................ 635
Chapter 4: Using SharePoint ......................................................................................................... 655

Book IX: Managing Linux Systems ................................... 669
Chapter 1: Installing a Linux Server ............................................................................................. 671
Chapter 2: Getting Used to Linux ................................................................................................. 685
Chapter 3: Basic Linux Network Configuration .......................................................................... 693
Chapter 4: Running DHCP and DNS .............................................................................................. 707
Chapter 5: Doing the Samba Dance .............................................................................................. 717
Chapter 6: Running Apache........................................................................................................... 731
Chapter 7: Running Sendmail ........................................................................................................ 743
Chapter 8: Running FTP ................................................................................................................. 753
Chapter 9: Linux Commands ......................................................................................................... 759

Appendix A: Directory of Useful Web Sites ....................... 787
Appendix B: Glossary...................................................... 795
Index ............................................................................. 823
                  Table of Contents
Introduction........................................................................ 1
           About This Book .............................................................................................. 2
           How to Use This Book ..................................................................................... 3
           How This Book Is Organized .......................................................................... 3
                Book I: Networking Basics .................................................................... 3
                Book II: Building a Network .................................................................. 4
                Book III: Network Administration and Security ................................. 4
                Book IV: TCP/IP and the Internet ......................................................... 4
                Book V: Wireless Networking ............................................................... 4
                Book VI: Mobile Networking ................................................................. 4
                Book VII: Windows Server 2008 R2 Reference .................................... 5
                Book VIII: Using Other Windows Servers ............................................ 5
                Book IX: Managing Linux Systems ....................................................... 5
           Icons Used in This Book ................................................................................. 5
           Where to Go from Here ................................................................................... 6


Book I: Networking Basics ................................................... 7
     Chapter 1: Understanding Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
           What Is a Network? .......................................................................................... 9
                 Network building blocks ..................................................................... 10
                 Why bother? ......................................................................................... 12
           Of Clients and Servers................................................................................... 13
           Dedicated Servers and Peers ....................................................................... 14
           Networks Big and Small ................................................................................ 14
           Network Topology ......................................................................................... 15
                 Bus topology......................................................................................... 15
                 Star topology ........................................................................................ 16
                 Expanding stars.................................................................................... 17
                 Ring topology ....................................................................................... 18
                 Mesh topology ...................................................................................... 18

     Chapter 2: Understanding Network Protocols and Standards. . . . . . .21
           Understanding Protocols.............................................................................. 21
           Understanding Standards ............................................................................. 23
           The Seven Layers of the OSI Reference Model .......................................... 24
                The Physical Layer .............................................................................. 25
                The Data Link Layer............................................................................. 26
xii   Networking All-in-One For Dummies, 4th Edition


                 The Network Layer .............................................................................. 28
                 The Transport Layer ........................................................................... 30
                 The Session Layer ................................................................................ 32
                 The Presentation Layer ....................................................................... 32
                 The Application Layer ......................................................................... 33
            Following a Packet through the Layers ...................................................... 33
            The Ethernet Protocol .................................................................................. 34
                 Standard Ethernet ................................................................................ 35
                 Fast Ethernet ........................................................................................ 36
                 Gigabit Ethernet ................................................................................... 37
            The TCP/IP Protocol Suite ............................................................................ 37
                 IP ............................................................................................................ 38
                 TCP ........................................................................................................ 39
                 UDP ........................................................................................................ 40
            Other Protocols Worth Knowing About ..................................................... 41

       Chapter 3: Understanding Network Hardware . . . . . . . . . . . . . . . . . . . .43
            Servers ............................................................................................................ 43
                 What’s important in a server.............................................................. 43
                 Components of a server computer .................................................... 44
                 Server form factors .............................................................................. 46
            Network Interface Cards ............................................................................... 48
            Network Cable ................................................................................................ 48
                 Coaxial cable ........................................................................................ 49
                 Twisted-pair cable ............................................................................... 50
            Switches .......................................................................................................... 51
            Repeaters ........................................................................................................ 54
            Bridges ............................................................................................................ 55
            Routers............................................................................................................ 57
            Network Attached Storage ........................................................................... 58
            Network Printers ........................................................................................... 59

       Chapter 4: Understanding Network Operating Systems . . . . . . . . . . . .61
            Network Operating System Features .......................................................... 61
                 Network support .................................................................................. 61
                 File-sharing services ............................................................................ 62
                 Multitasking .......................................................................................... 62
                 Directory services................................................................................ 64
                 Security services .................................................................................. 64
            Microsoft’s Server Operating Systems ....................................................... 65
                 Windows 2000 Server .......................................................................... 66
                 Windows Server 2003 .......................................................................... 66
                 Windows Server 2008 .......................................................................... 68
                 Windows Server 2008 R2 ..................................................................... 68
            Other Server Operating Systems ................................................................. 68
                 Linux ...................................................................................................... 69
                 Apple Mac OS/X Server ....................................................................... 69
                 Novell NetWare .................................................................................... 69
                                                                                 Table of Contents                     xiii

           Peer-to-Peer Networking with Windows ..................................................... 70
                 Advantages of peer-to-peer networks ............................................... 70
                 Drawbacks of peer-to-peer networks ................................................ 71
                 Windows 7............................................................................................. 71
                 Windows Vista ...................................................................................... 72
                 Older Windows versions ..................................................................... 73


Book II: Building a Network .............................................. 75
     Chapter 1: Planning a Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
           Making a Network Plan ................................................................................. 77
           Being Purposeful............................................................................................ 78
           Taking Stock ................................................................................................... 79
                What you need to know ...................................................................... 79
                Programs that gather information for you ....................................... 83
           To Dedicate or Not to Dedicate: That Is the Question.............................. 84
           Types of Servers ............................................................................................ 84
                File servers............................................................................................ 84
                Print servers ......................................................................................... 85
                Web servers .......................................................................................... 85
                Mail servers .......................................................................................... 85
                Database servers.................................................................................. 85
           Choosing a Server Operating System.......................................................... 86
           Planning the Infrastructure .......................................................................... 86
           Drawing Diagrams ......................................................................................... 87
           Sample Network Plans .................................................................................. 88
                Building a small network: California Sport Surface, Inc. ................. 88
                Connecting two networks: Creative Course Development, Inc...... 90
                Improving network performance: DCH Accounting ........................ 92

     Chapter 2: Installing Network Hardware. . . . . . . . . . . . . . . . . . . . . . . . .95
           Installing a Network Interface Card ............................................................. 95
           Installing Twisted-Pair Cable........................................................................ 97
                 Cable categories ................................................................................... 97
                 What’s with the pairs? ......................................................................... 98
                 To shield or not to shield ................................................................... 98
                 When to use plenum cable ................................................................. 99
                 Sometimes solid, sometimes stranded ............................................. 99
                 Installation guidelines ....................................................................... 100
                 Getting the tools that you need ....................................................... 101
                 Pinouts for twisted-pair cables ........................................................ 102
                 Attaching RJ-45 connectors .............................................................. 103
                 Crossover cables................................................................................ 105
                 Wall jacks and patch panels ............................................................. 105
xiv   Networking All-in-One For Dummies, 4th Edition


             Installing Coaxial Cable ............................................................................... 107
             Attaching a BNC Connector to Coaxial Cable .......................................... 108
             Installing Switches ....................................................................................... 109
             Daisy-Chaining Switches ............................................................................. 109

       Chapter 3: Setting Up a Network Server . . . . . . . . . . . . . . . . . . . . . . . .111
             The Many Ways to Install a Network Operating System ........................ 111
                   Full install versus upgrade................................................................ 111
                   Installing over the network ............................................................... 112
                   Automated and remote installations ............................................... 113
             Gathering Your Stuff.................................................................................... 114
                   A capable server computer .............................................................. 114
                   The server operating system ........................................................... 115
                   Other software ................................................................................... 115
                   A working Internet connection......................................................... 115
                   A good book........................................................................................ 116
             Making Informed Decisions ........................................................................ 116
             Final Preparations ....................................................................................... 117
             Installing a Network Operating System .................................................... 117
                   Phase 1: Collecting Information ....................................................... 118
                   Phase 2: Installing Windows ............................................................. 118
             Configuring Your Server ............................................................................. 119

       Chapter 4: Configuring Windows Clients. . . . . . . . . . . . . . . . . . . . . . . .121
             Configuring Network Connections ............................................................ 121
                  Configuring Windows XP network connections ............................. 122
                  Configuring Windows Vista network connections......................... 126
                  Configuring Windows 7 network connections ............................... 128
             Configuring Client Computer Identification ............................................. 130
                  Configuring Windows XP computer identification ........................ 131
                  Configuring Windows Vista or Windows 7 computer
                    identification ................................................................................... 132
             Configuring Network Logon ....................................................................... 134

       Chapter 5: Macintosh Networking . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135
             What You Need to Know to Hook Up a Macintosh Network .................. 135
                 Mac networking protocols ................................................................ 135
                 Mac OS X Server ................................................................................. 136
             What You Need to Know to Use a Macintosh Network .......................... 137
                 Configuring a Mac for networking ................................................... 137
                 Accessing a network printer............................................................. 138
                 Sharing files with other users........................................................... 138
                 Accessing shared files ....................................................................... 139
             What You Need to Know to Network Macintoshes with PCs................. 139
                                                                                 Table of Contents                        xv

    Chapter 6: Configuring Other Network Features . . . . . . . . . . . . . . . . .141
           Configuring Network Printers .................................................................... 141
                Adding a network printer.................................................................. 141
                Accessing a network printer using a Web interface ...................... 143
           Configuring Internet Access ....................................................................... 145
                Configuring clients for DHCP ............................................................ 145
                Using Internet Connection Sharing .................................................. 147
           Mapping Network Drives ............................................................................ 147

    Chapter 7: Verifying Your Network Installation . . . . . . . . . . . . . . . . . .151
           Is the Computer Connected to the Network?........................................... 151
           Is the Network Configuration Working? .................................................... 152
           Can the Computers Ping Each Other?....................................................... 154
           Can You Log On?.......................................................................................... 154
           Are Network Drives Mapped Correctly? ................................................... 155
           Do Network Printers Work?........................................................................ 155

    Chapter 8: Going Virtual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157
           Understanding Virtualization ..................................................................... 157
           Looking at the Benefits of Virtualization .................................................. 159
           Getting Started with Virtualization............................................................ 161
           Creating a Virtual Machine ......................................................................... 162


Book III: Network Administration and Security ................. 169
    Chapter 1: Help Wanted: Job Description for a
    Network Administrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .171
           Knowing What Network Administrators Do ............................................. 171
           Choosing the Part-Time Administrator..................................................... 173
           Establishing Routine Chores ...................................................................... 174
           Managing Network Users ............................................................................ 175
           Patching Up Your Operating System and Software................................. 175
           Discovering Software Tools for Network Administrators ...................... 176
           Building a Library ........................................................................................ 178
           Getting Certified ........................................................................................... 179
                 CompTIA ............................................................................................. 180
                 Microsoft ............................................................................................. 180
                 Cisco .................................................................................................... 181
           Gurus Need Gurus, Too .............................................................................. 181
           Helpful Bluffs and Excuses ......................................................................... 182
xvi   Networking All-in-One For Dummies, 4th Edition


       Chapter 2: Security 101 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
              Do You Need Security? ............................................................................... 186
              Considering Two Approaches to Security................................................ 187
              Physical Security: Locking Your Doors .................................................... 187
              Securing User Accounts .............................................................................. 189
                   Obfuscating your usernames ........................................................... 189
                   Using passwords wisely .................................................................... 190
                   A Password Generator For Dummies .............................................. 191
                   Securing the Administrator account ............................................... 192
              Hardening Your Network ............................................................................ 192
                   Using a firewall ................................................................................... 192
                   Disabling unnecessary services ....................................................... 193
                   Patching your servers ....................................................................... 193
              Securing Your Users .................................................................................... 193

       Chapter 3: Managing User Accounts . . . . . . . . . . . . . . . . . . . . . . . . . . .195
              Exploring What User Accounts Consist Of ............................................... 195
              Looking at Built-In Accounts ...................................................................... 196
                   The Administrator account .............................................................. 196
                   The Guest account ............................................................................. 197
                   Service accounts ................................................................................ 197
              Assigning User Rights ................................................................................. 198
              Controlling User Access with Permissions (Who Gets What) ............... 199
              Assigning Permissions to Groups .............................................................. 200
              Understanding User Profiles ...................................................................... 201
              Automating Tasks with Logon Scripts ...................................................... 201

       Chapter 4: Firewalls and Virus Protection. . . . . . . . . . . . . . . . . . . . . . .203
              Firewalls ........................................................................................................ 203
              The Many Types of Firewalls ..................................................................... 205
                   Packet filtering ................................................................................... 205
                   Stateful packet inspection (SPI) ....................................................... 207
                   Circuit-level gateway ......................................................................... 207
                   Application gateway .......................................................................... 208
              The Built-In Windows Firewall ................................................................... 208
              Virus Protection........................................................................................... 210
                   What is a virus? .................................................................................. 210
                   Antivirus programs ............................................................................ 211
                   Safe computing ................................................................................... 212
              Using Windows Action Center ................................................................... 213

       Chapter 5: Extending Your Network with VPN Access. . . . . . . . . . . .215
              Understanding VPN ..................................................................................... 215
              Looking at VPN Security ............................................................................. 216
              Understanding VPN Servers and Clients .................................................. 217
                                                                          Table of Contents                   xvii

Chapter 6: Managing Network Software. . . . . . . . . . . . . . . . . . . . . . . .221
      Understanding Software Licenses ............................................................. 222
      Using a License Server ................................................................................ 224
      Options for Deploying Network Software ................................................. 226
           Deploying software manually ........................................................... 226
           Running Setup from a network share .............................................. 226
           Installing silently ................................................................................ 227
           Creating an administrative installation image ............................... 229
           Pushing out software with group policy ......................................... 229
      Keeping Software Up to Date ..................................................................... 230

Chapter 7: Solving Network Problems . . . . . . . . . . . . . . . . . . . . . . . . . .233
      When Bad Things Happen to Good Computers ....................................... 234
      Fixing Dead Computers ............................................................................... 235
      Ways to Check a Network Connection...................................................... 236
      A Bunch of Error Messages Just Flew By!................................................. 237
      Double-Checking Your Network Settings ................................................. 237
      Using the Windows Networking Troubleshooter .................................... 238
      Time to Experiment ..................................................................................... 239
      Who’s on First? ............................................................................................ 240
      Restarting a Client Computer..................................................................... 240
      Booting in Safe Mode .................................................................................. 242
      Using System Restore ................................................................................. 242
      Restarting Network Services ...................................................................... 244
      Restarting a Network Server ...................................................................... 245
      Looking at Event Logs ................................................................................. 246
      Documenting Your Trials and Tribulations ............................................. 247

Chapter 8: Network Performance Anxiety. . . . . . . . . . . . . . . . . . . . . . .249
      Why Administrators Hate Performance Problems .................................. 249
      What Exactly Is a Bottleneck? .................................................................... 250
      The Five Most Common Network Bottlenecks ........................................ 252
           The hardware inside your servers .................................................. 252
           The server’s configuration options ................................................. 252
           Servers that do too much ................................................................. 253
           The network infrastructure .............................................................. 254
           Malfunctioning components ............................................................. 254
      Tuning Your Network the Compulsive Way ............................................. 255
      Monitoring Network Performance ............................................................. 256
      More Performance Tips .............................................................................. 258

Chapter 9: Backing Up Your Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .259
      Backing Up Your Data ................................................................................. 259
      All about Tapes and Tape Drives .............................................................. 260
xviii   Networking All-in-One For Dummies, 4th Edition


               Backup Software .......................................................................................... 261
               Types of Backups ........................................................................................ 262
                    Normal backups ................................................................................. 263
                    Copy backups ..................................................................................... 264
                    Daily backups ..................................................................................... 264
                    Incremental backups ......................................................................... 264
                    Differential backups........................................................................... 265
               Local versus Network Backups.................................................................. 266
               How Many Sets of Backups Should You Keep? ........................................ 267
               A Word about Tape Reliability................................................................... 268
               About Cleaning the Heads .......................................................................... 269
               Backup Security ........................................................................................... 270

         Chapter 10: Disaster Recovery and Business Continuity Planning . . . 271
               Assessing Different Types of Disasters..................................................... 272
                    Environmental disasters ................................................................... 272
                    Deliberate disasters ........................................................................... 273
                    Disruption of services ....................................................................... 273
                    Equipment failure .............................................................................. 274
                    Other disasters................................................................................... 274
               Analyzing the Impact of a Disaster ............................................................ 275
               Developing a Business Continuity Plan .................................................... 276
               Holding a Fire Drill....................................................................................... 277


    Book IV: TCP/IP and the Internet...................................... 279
         Chapter 1: Introduction to TCP/IP and the Internet . . . . . . . . . . . . . . .281
               What Is the Internet? ................................................................................... 281
               A Little Internet History .............................................................................. 283
               TCP/IP Standards and RFCs ....................................................................... 284
               The TCP/IP Protocol Framework ............................................................... 286
                     Network Interface layer..................................................................... 286
                     Network layer ..................................................................................... 287
                     Transport layer .................................................................................. 287
                     Application layer ................................................................................ 288

         Chapter 2: Understanding IP Addresses . . . . . . . . . . . . . . . . . . . . . . . .289
               Understanding Binary ................................................................................. 289
                     Counting by ones ............................................................................... 289
                     Doing the logic thing ......................................................................... 291
                     Working with the binary Windows Calculator ............................... 292
               Introducing IP Addresses ........................................................................... 293
                     Networks and hosts ........................................................................... 294
                     The dotted-decimal dance ................................................................ 294
                                                                             Table of Contents                      xix

       Classifying IP Addresses ............................................................................. 295
            Class A addresses .............................................................................. 297
            Class B addresses .............................................................................. 299
            Class C addresses .............................................................................. 299
       Subnetting..................................................................................................... 299
            Subnets ................................................................................................ 300
            Subnet masks...................................................................................... 300
            Network prefix notation .................................................................... 302
            Default subnets .................................................................................. 302
            The great subnet roundup ................................................................ 303
            IP block parties .................................................................................. 303
            Private and public addresses ........................................................... 304
       Network Address Translation .................................................................... 305

Chapter 3: Using DHCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .307
       Understanding DHCP .................................................................................. 307
            Configuration information provided by DHCP ............................... 307
            DHCP servers...................................................................................... 308
            How DHCP actually works ................................................................ 308
       Understanding Scopes ................................................................................ 310
            Feeling excluded? ............................................................................... 311
            Reservations suggested .................................................................... 311
            How long to lease? ............................................................................. 312
       Working with a DHCP Server...................................................................... 313
            Installing and configuring a DHCP server ....................................... 313
            Managing a DHCP server................................................................... 316
       How to Configure a Windows DHCP Client............................................... 318
            Automatic Private IP Addressing ..................................................... 319
            Renewing and releasing leases......................................................... 319

Chapter 4: Using DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .321
       Understanding DNS Names ........................................................................ 321
            Domains and domain names ............................................................ 322
            Fully qualified domain names........................................................... 323
       Top-Level Domains ...................................................................................... 324
            Generic domains ................................................................................ 324
            Geographic domains.......................................................................... 325
       The Hosts File .............................................................................................. 327
       Understanding DNS Servers and Zones .................................................... 330
            Zones ................................................................................................... 330
            Primary and secondary servers ....................................................... 332
            Root servers ....................................................................................... 332
            Caching................................................................................................ 335
       Understanding DNS Queries....................................................................... 335
            A real-life DNS example ..................................................................... 336
xx   Networking All-in-One For Dummies, 4th Edition


             Zone Files and Resource Records ............................................................. 337
                  SOA records ........................................................................................ 339
                  NS records .......................................................................................... 340
                  A records............................................................................................. 340
                  CNAME records .................................................................................. 341
                  PTR records ........................................................................................ 341
                  MX records ......................................................................................... 342
             Reverse Lookup Zones ................................................................................ 342
             Working with the Windows DNS Server.................................................... 343
             How to Configure a Windows DNS Client ................................................. 345

      Chapter 5: Using FTP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .347
             Discovering FTP ........................................................................................... 347
             Configuring an FTP Server .......................................................................... 348
                  Installing FTP ...................................................................................... 348
                  Creating an FTP site........................................................................... 348
                  Changing the FTP site properties .................................................... 351
                  Adding content to your FTP site ...................................................... 353
             Accessing an FTP Site with a Browser ...................................................... 354
             Using an FTP Command Line Client .......................................................... 355
             FTP Command and Subcommand Reference ........................................... 358
                  The FTP command ............................................................................. 358
                  ! (Escape) ............................................................................................ 359
                  ? (Help) ................................................................................................ 359
                  append................................................................................................. 359
                  ascii ...................................................................................................... 360
                  bell ....................................................................................................... 360
                  binary .................................................................................................. 360
                  bye ....................................................................................................... 360
                  cd ......................................................................................................... 360
                  close..................................................................................................... 361
                  debug ................................................................................................... 361
                  delete ................................................................................................... 361
                  dir ......................................................................................................... 361
                  disconnect .......................................................................................... 362
                  get ........................................................................................................ 362
                  glob ...................................................................................................... 362
                  hash ..................................................................................................... 363
                  help ...................................................................................................... 363
                  lcd ........................................................................................................ 363
                  literal ................................................................................................... 363
                  ls .......................................................................................................... 364
                  mdelete................................................................................................ 364
                  mdir ..................................................................................................... 364
                  mget ..................................................................................................... 364
                  mkdir ................................................................................................... 365
                                                                              Table of Contents                        xxi

              mls ....................................................................................................... 365
              mput .................................................................................................... 365
              open ..................................................................................................... 365
              prompt................................................................................................. 366
              put ........................................................................................................ 366
              pwd ...................................................................................................... 366
              quit ....................................................................................................... 367
              quote.................................................................................................... 367
              recv ...................................................................................................... 367
              remotehelp ......................................................................................... 368
              rename................................................................................................. 368
              rmdir .................................................................................................... 368
              send ..................................................................................................... 368
              status ................................................................................................... 369
              trace ..................................................................................................... 369
              type ...................................................................................................... 369
              user ...................................................................................................... 370
              verbose................................................................................................ 370

Chapter 6: TCP/IP Tools and Commands . . . . . . . . . . . . . . . . . . . . . . . .371
      Using the arp Command ............................................................................. 371
      Using the hostname Command .................................................................. 372
      Using the ipconfig Command ..................................................................... 373
           Displaying basic IP configuration .................................................... 373
           Displaying detailed configuration information .............................. 374
           Renewing an IP lease ......................................................................... 374
           Releasing an IP lease ......................................................................... 375
           Flushing the local DNS cache ........................................................... 375
      Using the nbtstat Command....................................................................... 375
      Using the netdiag Utility ............................................................................. 377
      Using the netstat Command ....................................................................... 378
           Displaying connections ..................................................................... 379
           Displaying interface statistics .......................................................... 379
      Using the nslookup Command ................................................................... 382
           Looking up an IP address .................................................................. 382
           Using nslookup subcommands ........................................................ 383
           Displaying DNS records .................................................................... 384
           Locating the mail server for an e-mail address .............................. 385
           Taking a ride through DNS-Land ...................................................... 386
      Using the pathping Command ................................................................... 389
      Using the ping Command ........................................................................... 390
      Using the route Command.......................................................................... 391
           Displaying the routing table ............................................................. 391
           Modifying the routing table .............................................................. 394
      Using the tracert Command ....................................................................... 395
xxii      Networking All-in-One For Dummies, 4th Edition


       Book V: Wireless Networking ........................................... 397
            Chapter 1: Setting Up a Wireless Network . . . . . . . . . . . . . . . . . . . . . .399
                  Diving into Wireless Networking ............................................................... 400
                  A Little High School Electronics ................................................................ 400
                        Waves and frequencies ..................................................................... 401
                        Wavelength and antennas................................................................. 402
                        Spectrums and the FCC ..................................................................... 402
                  Eight-Oh-Two-Dot-Eleventy Something? (Or, Understanding
                    Wireless Standards)................................................................................. 404
                  Home on the Range ..................................................................................... 405
                  Wireless Network Adapters........................................................................ 406
                  Wireless Access Points ............................................................................... 407
                        Infrastructure mode .......................................................................... 408
                        Multifunction WAPs ........................................................................... 409
                  Roaming ........................................................................................................ 410
                        Wireless bridging ............................................................................... 410
                        Ad-hoc networks ................................................................................ 411
                  Configuring a Wireless Access Point ......................................................... 411
                        Basic configuration options.............................................................. 411
                        DHCP configuration ........................................................................... 413
                  Configuring Windows XP for Wireless Networking ................................. 414
                  Using a Wireless Network with Windows XP ........................................... 415
                  Connecting to a Wireless Network with Windows Vista ........................ 417
                  Connecting to a Wireless Network with Windows 7 ............................... 417

            Chapter 2: Securing a Wireless Network . . . . . . . . . . . . . . . . . . . . . . .419
                  Understanding Wireless Security Threats................................................ 419
                       Intruders ............................................................................................. 420
                       Freeloaders ......................................................................................... 421
                       Eavesdroppers ................................................................................... 421
                       Spoilers................................................................................................ 422
                       Rogue access points .......................................................................... 422
                  What About Wardrivers and Warchalkers?.............................................. 423
                       Wardriving .......................................................................................... 423
                       Warchalking ........................................................................................ 424
                  Securing Your Wireless Network ............................................................... 425
                       Changing the password..................................................................... 425
                       Securing the SSID ............................................................................... 425
                       Enabling WEP ..................................................................................... 427
                       Using WPA........................................................................................... 428
                       Using MAC address filtering ............................................................. 429
                       Placing your access points outside the firewall ............................ 430
                                                                                 Table of Contents                  xxiii

     Chapter 3: Hotspotting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .431
            What Is a Hotspot? ...................................................................................... 431
            What’s So Great about Hotspots? .............................................................. 432
            Safe Hotspotting .......................................................................................... 432
            Free Hotspots ............................................................................................... 432
            Fee-Based Hotspots ..................................................................................... 433
                  T-Mobile .............................................................................................. 434
                  Boingo ................................................................................................. 434
            Setting Up Your Own Hotspot .................................................................... 434

     Chapter 4: Troubleshooting a Wireless Network. . . . . . . . . . . . . . . . .437
            Checking for Obvious Problems ................................................................ 437
            Pinpointing the Problem ............................................................................. 438
            Changing Channels ...................................................................................... 438
            Fiddle with the Antennas ............................................................................ 439
            Adding Another Access Point .................................................................... 440
            Help! I Forgot My Router’s Password! ....................................................... 441

     Chapter 5: Wireless Networking with Bluetooth. . . . . . . . . . . . . . . . .443
            Understanding Bluetooth ........................................................................... 443
            Bluetooth Technical Stuff ........................................................................... 444
            How to Add Bluetooth to Your Computer ................................................ 445
            Using Bluetooth in Windows ...................................................................... 445
            Installing a USB Bluetooth Adapter ........................................................... 446
            Enabling Discovery ...................................................................................... 446
            Installing a Bluetooth Mouse or Keyboard............................................... 447


Book VI: Mobile Networking ............................................ 449
     Chapter 1: Managing Mobile Devices . . . . . . . . . . . . . . . . . . . . . . . . . .451
            The Many Types of Mobile Devices .......................................................... 451
            Considering Security for Mobile Devices ................................................. 453

     Chapter 2: Managing BlackBerry Devices . . . . . . . . . . . . . . . . . . . . . .455
            Understanding BlackBerry ......................................................................... 455
            Adding a BES User ....................................................................................... 458
            Locking and Erasing a Handheld ............................................................... 460

     Chapter 3: Managing iPhone Devices . . . . . . . . . . . . . . . . . . . . . . . . . .461
            Understanding the iPhone .......................................................................... 461
            Integrating iPhone with Exchange ............................................................. 462
                  Enabling Exchange Mobile Services ................................................ 463
                  Enabling ActiveSync for a user’s mailbox....................................... 464
                  Configuring the iPhone for Exchange e-mail .................................. 465
xxiv   Networking All-in-One For Dummies, 4th Edition


        Chapter 4: Managing Android Devices . . . . . . . . . . . . . . . . . . . . . . . . .469
              Understanding Android Phones ................................................................ 469
              Looking at the Android Operating System ............................................... 470
              Perusing Android’s Core Applications...................................................... 471
              Integrating Android with Exchange........................................................... 471

        Chapter 5: Managing Netbooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .473
              Understanding Netbook Computers ......................................................... 473
              Connecting with a Netbook ........................................................................ 474
              Tips for Using a Netbook Effectively ......................................................... 476


   Book VII: Windows Server 2008 Reference ....................... 477
        Chapter 1: Installing and Configuring Windows Server 2008 R2 . . . .479
              Planning a Windows Server Installation ................................................... 479
                   Checking system requirements........................................................ 479
                   Reading the release notes ................................................................. 480
                   Deciding whether to upgrade or install .......................................... 481
                   Considering your licensing options................................................. 481
                   Thinking about multiboot ................................................................. 481
                   Choosing a file system....................................................................... 482
                   Planning your partitions ................................................................... 483
                   Deciding your TCP/IP configuration ................................................ 484
                   Choosing workgroups or domains .................................................. 485
              Before You Install . . . .................................................................................. 485
                   Backing up .......................................................................................... 486
                   Checking the event logs .................................................................... 486
                   Uncompressing data .......................................................................... 486
                   Disconnecting UPS devices............................................................... 486
              Running Setup .............................................................................................. 486
              Adding Server Roles and Features ............................................................ 489

        Chapter 2: Managing Windows Server 2008 . . . . . . . . . . . . . . . . . . . . .493
              Using the Administrator Account .............................................................. 493
              Using Remote Desktop Connection ........................................................... 494
                   Enabling remote access .................................................................... 494
                   Connecting remotely ......................................................................... 495
              Using Microsoft Management Console ..................................................... 497
                   Working with MMC ............................................................................ 497
                   An overview of the MMC consoles .................................................. 498
              Customizing MMC........................................................................................ 501
                   Adding snap-ins .................................................................................. 501
                   Adding taskpads................................................................................. 502
                                                                            Table of Contents                     xxv

Chapter 3: Dealing with Active Directory . . . . . . . . . . . . . . . . . . . . . . .509
      What Directories Do .................................................................................... 509
      Remembering the Good-Ol’ Days of NT Domains .................................... 510
           PDCs and BDCs................................................................................... 510
           Trusts .................................................................................................. 511
           NetBIOS names ................................................................................... 511
      Active Directory to the Rescue .................................................................. 511
      Understanding How Active Directory Is Structured ............................... 512
           Objects ................................................................................................ 512
           Domains .............................................................................................. 513
           Organizational units .......................................................................... 514
           Trees .................................................................................................... 514
           Forests ................................................................................................. 515
      Creating a Domain ....................................................................................... 516
      Creating an Organizational Unit ................................................................ 516

Chapter 4: Managing Windows User Accounts . . . . . . . . . . . . . . . . . .519
      Understanding Windows User Accounts .................................................. 519
            Local accounts versus domain accounts........................................ 519
            User account properties ................................................................... 520
      Creating a New User .................................................................................... 520
      Setting User Properties ............................................................................... 523
            Changing the user’s contact information ....................................... 524
            Setting account options .................................................................... 524
            Specifying logon hours ...................................................................... 525
            Restricting access to certain computers ........................................ 526
            Setting the user’s profile information ............................................. 527
      Resetting User Passwords .......................................................................... 528
      Disabling and Enabling User Accounts ..................................................... 529
      Deleting a User ............................................................................................. 529
      Working with Groups .................................................................................. 530
            Group types ........................................................................................ 530
            Group scope ....................................................................................... 530
            Default groups .................................................................................... 531
            Creating a group................................................................................. 533
            Adding a member to a group ............................................................ 534
      User Profiles ................................................................................................. 535
            Types of user profiles ........................................................................ 536
            Creating a roaming profile ................................................................ 536
      Creating a Logon Script .............................................................................. 538

Chapter 5: Managing a File Server . . . . . . . . . . . . . . . . . . . . . . . . . . . . .539
      Understanding Permissions ....................................................................... 539
      Understanding Shares ................................................................................. 541
      Configuring the File Server Role ................................................................ 542
xxvi   Networking All-in-One For Dummies, 4th Edition


               Managing Your File Server ......................................................................... 542
                   Using the Provision a Shared Folder Wizard .................................. 543
                   Sharing a folder without the wizard ................................................ 548
                   Granting permissions ........................................................................ 549

        Chapter 6: Using Group Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .553
               Understanding Group Policy ...................................................................... 553
               Enabling Group Policy Management on Windows Server 2008 ............. 554
               Creating Group Policy Objects .................................................................. 555
               Filtering Group Policy Objects ................................................................... 560

        Chapter 7: Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .563
               Working with the Event Viewer ................................................................. 563
                    Using the Event Viewer ..................................................................... 564
                    Setting event log policies .................................................................. 565
               Monitoring Performance............................................................................. 566
                    Using the Reliability and Performance Monitor............................. 567
                    Creating performance logs ............................................................... 570
               Using the Computer Management Console .............................................. 572
               Working with Services ................................................................................ 573

        Chapter 8: Windows Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .575
               Using a Command Window ........................................................................ 575
                    Opening and closing a command window ...................................... 576
                    Editing commands ............................................................................. 576
                    Using the Control menu .................................................................... 577
               Special Command Tricks ............................................................................ 577
                    Wildcards ............................................................................................ 578
                    Chaining commands .......................................................................... 578
                    Redirection and piping ...................................................................... 579
                    Environment variables ...................................................................... 580
                    Batch files ........................................................................................... 581
               The EventCreate Command ....................................................................... 582
               Net Commands............................................................................................. 583
                    The Net Accounts command ............................................................ 584
                    The Net Computer command ........................................................... 585
                    The Net Config command ................................................................. 585
                    The Net Continue command............................................................. 586
                    The Net File command ...................................................................... 586
                    The Net Group command ................................................................. 587
                    The Net Help command .................................................................... 588
                    The Net Helpmsg command ............................................................. 589
                    The Net Localgroup command......................................................... 589
                    The Net Name command .................................................................. 591
                    The Net Pause command .................................................................. 591
                                                                                 Table of Contents                  xxvii

               The Net Print command .................................................................... 592
               The Net Send command .................................................................... 593
               The Net Session command ............................................................... 594
               The Net Share command................................................................... 594
               The Net Start command .................................................................... 596
               The Net Statistics command ............................................................ 596
               The Net Stop command..................................................................... 597
               The Net Time command.................................................................... 597
               The Net Use command ...................................................................... 598
               The Net User command .................................................................... 599
               The Net View command .................................................................... 601
          The RunAs Command ................................................................................. 602


Book VIII: Using Other Windows Servers ........................... 603
    Chapter 1: Using Internet Information System (IIS) . . . . . . . . . . . . . . .605
          Installing IIS .................................................................................................. 605
          Understanding the Default Web Site ......................................................... 608
          Creating Web Sites ...................................................................................... 610

    Chapter 2: Managing Exchange Server 2010. . . . . . . . . . . . . . . . . . . . .615
          Creating a Mailbox....................................................................................... 615
          Managing Mailboxes .................................................................................... 621
               Enabling Mailbox Features ............................................................... 622
               Creating a Forwarder......................................................................... 623
               Setting Mailbox Storage Limits......................................................... 625
          Configuring Outlook for Exchange ............................................................ 628
          Viewing Another Mailbox ........................................................................... 631

    Chapter 3: Using SQL Server 2008 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .635
          What Is a Database? .................................................................................... 635
          What Is a Relational Database? .................................................................. 636
          What Is SQL?................................................................................................. 637
                SQL dialects ........................................................................................ 637
                SQL statements .................................................................................. 637
                Using the select statement ............................................................... 638
          Installing SQL Server 2008 .......................................................................... 639
          Using the SQL Server 2008 Management Studio ...................................... 646
          Creating a New Database ............................................................................ 647
          Creating Tables ............................................................................................ 648
          Editing Tables .............................................................................................. 651
          Working with Queries ................................................................................. 652
          Working with Scripts ................................................................................... 653
xxviii   Networking All-in-One For Dummies, 4th Edition


          Chapter 4: Using SharePoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .655
                What Is SharePoint? .................................................................................... 655
                Connecting to a SharePoint Site ................................................................ 656
                Adding Users ................................................................................................ 657
                Adding and Removing Announcements.................................................... 661
                Creating New Pages ..................................................................................... 663
                Editing the Quick Launch Menu................................................................. 666
                Working with Document Libraries ............................................................ 667


   Book IX: Managing Linux Systems .................................... 669
          Chapter 1: Installing a Linux Server . . . . . . . . . . . . . . . . . . . . . . . . . . . .671
                Planning a Linux Server Installation.......................................................... 671
                      Checking system requirements........................................................ 671
                      Choosing a distribution..................................................................... 672
                      Thinking about multiboot ................................................................. 673
                      Planning your partitions ................................................................... 673
                      Deciding on your TCP/IP configuration .......................................... 674
                Installing Fedora 7 ....................................................................................... 675
                Using the Setup Agent ......................................................................................... 683

          Chapter 2: Getting Used to Linux . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .685
                Linux: It Isn’t Windows................................................................................ 685
                      X Window ............................................................................................ 685
                      Virtual consoles ................................................................................. 686
                      Understanding the file system ......................................................... 686
                On Again, Off Again ..................................................................................... 688
                      Logging on........................................................................................... 688
                      Logging off .......................................................................................... 689
                      Shutting down .................................................................................... 689
                Using GNOME ............................................................................................... 689
                Getting to a Command Shell ....................................................................... 690
                Managing User Accounts ............................................................................ 691

          Chapter 3: Basic Linux Network Configuration . . . . . . . . . . . . . . . . . .693
                Using the Network Configuration Program .............................................. 693
                Restarting Your Network ............................................................................ 697
                Working with Network Configuration Files .............................................. 698
                     The Network file ................................................................................. 699
                     The ifcfg files ...................................................................................... 700
                     The Hosts file ...................................................................................... 701
                     The resolv.conf file ............................................................................ 702
                     The nsswitch.conf file ....................................................................... 702
                     The xinetd.conf file ............................................................................ 703
                Displaying Your Network Configuration with the ifconfig Command ... 704
                                                                          Table of Contents                  xxix

Chapter 4: Running DHCP and DNS. . . . . . . . . . . . . . . . . . . . . . . . . . . . .707
      Running a DHCP Server............................................................................... 707
           Installing DHCP................................................................................... 708
           Configuring DHCP .............................................................................. 709
           Starting DHCP ..................................................................................... 710
      Running a DNS Server ................................................................................. 711
           Installing BIND .................................................................................... 711
           Looking at BIND configuration files ................................................. 712
           Restarting BIND .................................................................................. 716

Chapter 5: Doing the Samba Dance . . . . . . . . . . . . . . . . . . . . . . . . . . . .717
      Understanding Samba ................................................................................. 717
      Installing Samba ........................................................................................... 718
      Starting and Stopping Samba ..................................................................... 719
      Using the Samba Server Configuration Tool ............................................ 721
            Configuring server settings............................................................... 722
            Configuring Samba users .................................................................. 723
            Creating a share ................................................................................. 725
      Editing the smb.conf File ............................................................................ 727
      Using the Samba Client ............................................................................... 729

Chapter 6: Running Apache . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .731
      Installing Apache ......................................................................................... 731
      Starting and Stopping Apache ................................................................... 732
      Confirming that Apache Is Running .......................................................... 733
      Using the HTTP Configuration Tool .......................................................... 734
      Restricting Access to an Apache Server ................................................... 735
      Configuring Virtual Hosts ........................................................................... 736
            Configuring the default host ............................................................. 736
            Creating a virtual host ....................................................................... 739
      Setting the Apache User Account .............................................................. 740
      Manually Editing Apache’s Configuration Files ....................................... 741
      Creating Web Pages..................................................................................... 741

Chapter 7: Running Sendmail. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .743
      Understanding E-Mail .................................................................................. 743
      Installing Sendmail ...................................................................................... 744
      Modifying sendmail.mc ............................................................................... 745
            Enabling connections ........................................................................ 746
            Enabling masquerading..................................................................... 747
            Setting up aliases ............................................................................... 747
      Using SpamAssassin .................................................................................... 748
            Installing SpamAssassin .................................................................... 748
            Customizing SpamAssassin .............................................................. 749
            Blacklisting and whitelisting e-mail addresses .............................. 750
      Using the Mail Console Client .................................................................... 750
      Using Evolution ............................................................................................ 752
xxx   Networking All-in-One For Dummies, 4th Edition


       Chapter 8: Running FTP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .753
              Installing vsftpd ........................................................................................... 753
              Starting the vsftpd Service ......................................................................... 754
              Configuring FTP ........................................................................................... 754

       Chapter 9: Linux Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .759
              Command Shell Basics ................................................................................ 759
                   Getting to a shell ................................................................................ 760
                   Editing commands ............................................................................. 761
                   Wildcards ............................................................................................ 761
                   Redirection and piping ...................................................................... 762
                   Environment variables ...................................................................... 762
                   Shell scripts ........................................................................................ 763
              Directory and File Handling Commands ................................................... 764
                   The pwd command ............................................................................ 764
                   The cd command ............................................................................... 765
                   The mkdir command ......................................................................... 765
                   The rmdir command.......................................................................... 766
                   The ls command................................................................................. 766
                   The cp command ............................................................................... 767
                   The rm command............................................................................... 768
                   The mv command .............................................................................. 769
                   The touch command ......................................................................... 769
                   The cat command .............................................................................. 770
              Commands for Working with Packages and Services ............................. 771
                   The service command ....................................................................... 771
                   The rpm command ............................................................................ 773
              Commands for Administering Users ......................................................... 774
                   The useradd command ..................................................................... 774
                   The usermod command .................................................................... 775
                   The userdel command ...................................................................... 776
                   The chage command ......................................................................... 776
                   The passwd command ...................................................................... 777
                   The newusers command ................................................................... 777
                   The groupadd command................................................................... 777
                   The groupdel command .................................................................... 778
                   The gpasswd command .................................................................... 778
              Commands for Managing Ownership and Permissions .......................... 779
                   The chown command ........................................................................ 779
                   The chgrp command ......................................................................... 780
                   The chmod command ....................................................................... 780
                                                                                    Table of Contents                     xxxi

           Networking Commands............................................................................... 781
               The hostname command .................................................................. 781
               The ifconfig command ....................................................................... 782
               The netstat command ....................................................................... 783
               The ping command ............................................................................ 784
               The route command .......................................................................... 785
               The traceroute command ................................................................. 786


Appendix A: Directory of Useful Web Sites ........................ 787
           Certification .................................................................................................. 787
           Hardware ...................................................................................................... 787
           Home and Small Business Networking ..................................................... 788
           Linux .............................................................................................................. 789
           Magazines ..................................................................................................... 789
           Microsoft....................................................................................................... 790
           Network Standards Organizations ............................................................ 790
           Reference ...................................................................................................... 791
           Search ........................................................................................................... 791
           TCP/IP and the Internet .............................................................................. 792
           Wireless Networking ................................................................................... 793
           Smartphones ................................................................................................ 794


Appendix B: Glossary ...................................................... 795

Index.............................................................................. 823
xxxii   Networking All-in-One For Dummies, 4th Edition
Introduction

W        elcome to the fourth edition of Networking All-in-One For Dummies,
         the one networking book that’s designed to replace an entire shelf
full of the dull and tedious networking books you’d otherwise have to buy.
This book contains all the basic and not-so-basic information you need to
know to get a network up and running and to stay on top of the network as
it grows, develops problems, and encounters trouble.

If you’re just getting started as a network administrator, this book is ideal.
As a network administrator, you have to know about a lot of different topics:
installing and configuring network hardware, installing and configuring net-
work operating systems, planning a network, working with TCP/IP, securing
your network, working with mobile devices, backing up your data, and many
others.

You can, and probably eventually will, buy separate books on each of these
topics. It won’t take long before your bookshelf is bulging with 10,000 or
more pages of detailed information about every imaginable nuance of net-
working. But before you’re ready to tackle each of those topics in depth,
you need to get a bird’s-eye picture. This book is the ideal way to do that.

And if you already own 10,000 pages or more of network information, you
may be overwhelmed by the amount of detail and wonder, “Do I really need
to read 1,000 pages about Bind to set up a simple DNS server?” or “Do I
really need a six-pound book to show me how to install Linux?” Truth is,
most 1,000-page networking books have about 100 or so pages of really
useful information — the kind you use every day — and about 900 pages of
excruciating details that apply mostly to networks at places like NASA and
the CIA.

The basic idea of this book is that I’ve tried to wring out the 100 or so most
useful pages of information on nine different networking topics: network
basics, building a network, network administration and security, trouble-
shooting and disaster planning, working with TCP/IP, home networking,
wireless networking, Windows server operating systems, and Linux.

So whether you’ve just been put in charge of your first network or you’re a
seasoned pro, you’ve found the right book.
2   About This Book


About This Book
       Networking All-in-One For Dummies, 4th Edition, is intended to be a reference
       for all the great things (and maybe a few not-so-great things) that you may
       need to know when you’re setting up and managing a network. You can, of
       course, buy a huge 1,000-page book on each of the networking topics cov-
       ered in this book. But then, who would you get to carry them home from the
       bookstore for you? And where would you find the shelf space to store them?
       In this book, you get the information you need all conveniently packaged for
       you in between one set of covers.

       This book doesn’t pretend to be a comprehensive reference for every detail
       of these topics. Instead, this book shows you how to get up and running fast
       so that you have more time to do the things you really want to do. Designed
       using the easy-to-follow For Dummies format, this book helps you get the
       information you need without laboring to find it.

       Networking All-in-One For Dummies, 4th Edition, is a big book made up of sev-
       eral smaller books — minibooks, if you will. Each of these minibooks covers
       the basics of one key element of network management, such as setting up
       network hardware, installing a network operating system, or troubleshoot-
       ing network problems. Whenever one big thing is made up of several smaller
       things, confusion is always a possibility. That’s why Networking All-in-One
       For Dummies, 4th Edition, is designed to have multiple access points (I hear
       an acronym coming on — MAP!) to help you find what you want. At the
       beginning of the book is a detailed table of contents that covers the entire
       book. Then, each minibook begins with a minitable of contents that shows
       you at a glance what chapters are included in that minibook. Useful run-
       ning heads appear at the top of each page to point out the topic discussed
       on that page. And handy thumb tabs run down the side of the pages to help
       you quickly find each minibook. Finally, a comprehensive index lets you find
       information anywhere in the entire book.

       This isn’t the kind of book you pick up and read from start to finish, as if it
       were a cheap novel. If I ever see you reading it at the beach, I’ll kick sand in
       your face. This book is more like a reference, the kind of book you can pick
       up, turn to just about any page, and start reading. You don’t have to memo-
       rize anything in this book. It’s a need-to-know book: You pick it up when
       you need to know something. Need to know how to set up a DHCP server in
       Windows? Pick up the book. Need to know how to create a user account in
       Linux? Pick up the book. Otherwise, put it down and get on with your life.
                                           How This Book Is Organized              3

How to Use This Book
       This book works like a reference. Start with the topic you want to find out
       about. Look for it in the table of contents or in the index to get going. The
       table of contents is detailed enough that you should be able to find most of
       the topics you’re looking for. If not, turn to the index, where you can find
       even more detail.

       Of course, the book is loaded with information, so if you want to take a brief
       excursion into your topic, you’re more than welcome. If you want to know
       the big security picture, read the whole chapter on security. If you just want
       to know how to make a decent password, read just the section on pass-
       words. You get the idea.

       Whenever I describe a message or information that you see on the screen, I
       present it as follows:

       A message from your friendly network

       If you need to type something, you see the text you need to type like this:
       Type this stuff. In this example, you type Type this stuff at the keyboard and
       press Enter. An explanation usually follows, just in case you’re scratching
       your head and grunting, “Huh?”



How This Book Is Organized
       Each of the nine minibooks contained in Networking All-in-One For Dummies,
       4th Edition, can stand by itself. The first minibook covers the networking
       basics that you should know to help you understand the rest of the stuff in
       this book. Of course, if you’ve been managing a network for awhile already,
       you probably know all this stuff, so you can probably skip Book I or just
       skim it quickly for laughs. The remaining minibooks cover a variety of net-
       working topics that you would normally find covered in separate books.
       Here’s a brief description of what you find in each minibook.


       Book I: Networking Basics
       This minibook covers the networking basics that you need to understand to
       get going. You find out what a network is, how networking standards work,
       what hardware components are required to make up a network, and what
       network operating systems do. You discover the difference between peer-to-
       peer networking and client-server networking. And you also get a compari-
       son of the most popular network operating systems, including the current
       incarnations of Windows Server and Linux.
4   How This Book Is Organized


       Book II: Building a Network
       In this minibook, you find the ins and outs of building a network. First, you see
       how to create a plan for your network. After all, planning is the first step of
       any great endeavor. Then, you discover how to install network hardware, such
       as network interface cards, and how to work with various types of networking
       cable. You receive some general pointers about installing a network server
       operating system. You gain insight into how to configure various versions of
       Windows to access a network. And finally, you get an overview of how virtual-
       ization technologies like VMWare can help you manage your servers.


       Book III: Network Administration and Security
       In this minibook, you discover what it means to be a network administra-
       tor, with an emphasis on how to secure your network so that it’s safe
       from intruders but at the same time allows your network’s users access to
       everything they need. In the real world, this responsibility isn’t as easy as
       it sounds. This minibook begins with an overview of what network adminis-
       trators do. Then, it describes some of the basic practices of good network
       security, such as using strong passwords and providing physical security for
       your servers. It includes detailed information about setting up and managing
       network user accounts, using virus scanners, setting up firewalls, backing up
       network data, keeping network software up to date, working with virtual pri-
       vate networks (VPNs), and troubleshooting common network problems.


       Book IV: TCP/IP and the Internet
       This minibook is devoted to the most popular network technology on the
       planet: TCP/IP. (Actually, it may be the most popular protocol in the uni-
       verse. The aliens in Independence Day had a TCP/IP network on their space-
       ship, enabling Will Smith and Jeff Goldblum to hack their way in. The aliens
       should have read the section on firewalls in Book III.)


       Book V: Wireless Networking
       In this minibook, you discover the ins and outs of setting up and securing a
       wireless network.


       Book VI: Mobile Networking
       This minibook is devoted to the special requirements for managing mobile
       users who want to connect to your network. Here, you’ll find chapters on
       working with the most popular types of smartphones, including Blackberry,
       iPhone, and Android devices, as well as information about incorporating net-
       books into your network.
                                                 Icons Used in This Book             5

       Book VII: Windows Server 2008 R2 Reference
       This minibook describes the basics of setting up and administering a server
       using the latest version of Windows Server 2008 R2. You also find helpful
       information about its predecessors, Windows Server 2008 and Windows
       Server 2003. You find chapters on installing a Windows server, managing
       user accounts, setting up a file server, and securing a Windows server. Plus,
       you find a handy reference to the many Windows networking commands
       that you can use from a command prompt.


       Book VIII: Using Other Windows Servers
       This minibook shows you the basics of setting up other popular Windows
       server products, including the IIS Web server, Exchange Server 2010 for man-
       aging e-mail, SQL Server 2008 for databases, and SharePoint 2010 for creating
       intranet sites.


       Book IX: Managing Linux Systems
       Linux has fast become an inexpensive alternative to Windows or NetWare. In
       this minibook, you discover the basics of installing and managing Linux. You
       find out how to install Fedora, work with Linux commands and GNOME (a
       popular graphical interface for Linux), configure Linux for networking, set up a
       Windows-compatible file server using Samba, and run popular Internet servers
       such as DHCP, Bind, and Sendmail. Plus, you get a concise Linux command ref-
       erence that will turn you into a Linux command line junkie in no time.



Icons Used in This Book
       Like any For Dummies book, this book is chock-full of helpful icons that draw
       your attention to items of particular importance. You find the following
       icons throughout this book:

       Hold it — technical stuff is just around the corner. Read on only if you have
       your pocket protector.



       Pay special attention to this icon; it lets you know that some particularly
       useful tidbit is at hand.



       Did I tell you about the memory course I took?
6   Where to Go from Here


       Danger, Will Robinson! This icon highlights information that may help you
       avert disaster.



Where to Go from Here
       Yes, you can get there from here. With this book in hand, you’re ready to
       plow right through the rugged networking terrain. Browse through the table
       of contents and decide where you want to start. Be bold! Be courageous! Be
       adventurous! And above all, have fun!
      Book I
Networking Basics
Contents at a Glance
      Chapter 1: Understanding Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

      Chapter 2: Understanding Network Protocols and Standards. . . . . . .21

      Chapter 3: Understanding Network Hardware . . . . . . . . . . . . . . . . . . . .43

      Chapter 4: Understanding Network Operating Systems . . . . . . . . . . . .61
      Chapter 1: Understanding
      Networks
      In This Chapter
      ✓ Introducing computer networks
      ✓ Finding out all about clients, servers, and peers
      ✓ Understanding the various types of networks
      ✓ Figuring out the disadvantages of networking




      T    he first computer network was invented when ancient mathematicians
           connected their abacuses (or is it abaci?) together with kite string so they
      could instantly share their abacus answers with each other. Over the years,
      computer networks became more and more sophisticated. Now, instead of
      string, networks use electrical cables, fiber-optic cables, or wireless radio
      signals to connect computers to each other. The purpose, however, has
      remained the same: sharing information and getting work done faster.

      This chapter describes the basics of what computer networking is and how
      it works.



What Is a Network?
      A network is nothing more than two or more computers connected to each
      other so that they can exchange information, such as e-mail messages or
      documents, or share resources, such as disk storage or printers. In most
      cases, this connection is made via electrical cables that carry the infor-
      mation in the form of electrical signals. But in some cases, other types of
      connections are used. For example, fiber-optic cables let computers com-
      municate at extremely high speeds by using impulses of light. Wireless net-
      works let computers communicate by using radio signals, so the computers
      aren’t restricted by physical cables.

      In addition to the hardware that comprises the network, a network also
      requires special software to enable communications. In the early days of
      networking, you had to add this software to each computer on the network.
      Nowadays, network support is built in to all major operating systems, includ-
      ing all current versions of Windows, Macintosh operating systems, and Linux.
10   What Is a Network?


        Network building blocks
        All networks, large or small, require specialized network hardware to make
        them work. For small networks, the hardware may consist of nothing more
        than a collection of computers that are equipped with network ports, a cable
        for each computer, and a network switch that all the computers plug in to
        via the cable. Larger networks probably have additional components, such
        as routers or repeaters.

        Small or large, all networks are built from the following basic building
        blocks:

         ✦ Client computers: The computers that end users use to access the
           resources of the network. Client computers are typically computers
           located on users’ desks. They usually run a desktop version of Windows
           such as Windows 7, Vista, or XP. In addition, the client computers usu-
           ally run some type of application software such as Microsoft Office.
           Client computers are sometimes referred to as workstations.
         ✦ Server computers: Computers that provide shared resources, such as
           disk storage and printers, as well as network services, such as e-mail
           and Internet access. Server computers typically run a specialized net-
           work operating system such as Windows Server 2008 or 2003, NetWare,
           or Linux, along with special software to provide network services. For
           example, a server may run Microsoft Exchange to provide e-mail ser-
           vices for the network, or it may run Apache Web Server so that the com-
           puter can serve Web pages.
         ✦ Network interface: An interface — sometimes called a network port —
           that’s installed in a computer to enable the computer to communicate
           over a network. Almost all network interfaces implement a networking
           standard called Ethernet.
            A network interface is sometimes called a NIC, which stands for network
            interface card, because in the early days of networking you actually had
            to install a separate circuit card in the computer to provide a network
            interface. Nowadays, nearly all computers come with network interfaces
            built in as an integral part of the computer’s motherboard. Although
            separate network cards are rarely required these days, the term NIC is
            still frequently used to refer to the network interface.
            It’s still common to install separate network interface cards to provide
            more than one network interface on a single computer, or to replace
            a built-in network interface that has malfunctioned without having to
            replace the entire motherboard.
         ✦ Cable: Computers in a network are usually physically connected to each
           other using cable. Although several types of cable have been popular
           over the years, most networks today use a type of cable called twisted-
           pair, also known by its official designation 10BaseT.
                                             What Is a Network?           11

   Twisted-pair cable is also sometimes referred to as Cat-5 or Cat-6 cable.     Book I
   These terms refer to the standards that determine the maximum speed          Chapter 1
   with which the cable can carry data, Cat-6 being rated for more speed
   than Cat-5.




                                                                                   Understanding
   Twisted-pair cable can also be referred to simply as copper, to distin-




                                                                                     Networks
   guish it from fiber-optic cable which is used for the highest-speed net-
   work connections. Fiber-optic cable uses strands of glass to transmit
   light signals at very high speeds.
   In many cases, the cables run through the walls and converge on a cen-
   tral room called a wiring closet. But for smaller networks, the cables are
   often just strung along the floor, hidden behind desks and other furni-
   ture whenever possible.
✦ Switches: Network cable usually doesn’t connect computers directly to
  each other. Instead, each computer is connected by cable to a device
  known as a switch. The switch, in turn, connects to the rest of the net-
  work. Each switch contains a certain number of ports, typically 8 or 16.
  Thus, you can use an eight-port switch to connect up to eight comput-
  ers. Switches can be connected to each other to build larger networks.
  For more information about switches, see the “Network Topology” sec-
  tion later in this chapter. (Older networks may use a more primitive type
  of device called a hub instead of a switch. A hub provides the same func-
  tion as a switch, but it isn’t as efficient. The term hub is sometimes used
  to mean switch, even though hubs and switches are not technically the
  same thing.)
✦ Wireless networks: In many networks, cables and switches are making
  way for wireless network connections, which enable computers to com-
  municate via radio signals. In a wireless network, radio transmitters
  and receivers take the place of cables. The main advantage of wireless
  networking is its flexibility. With a wireless network, you don’t have to
  run cables through walls or ceilings, and your client computers can be
  located anywhere within range of the network broadcast. The main dis-
  advantage of wireless networking is that it’s inherently less secure than
  a cabled network.
✦ Network software: Although network hardware is essential, what really
  makes a network work is software. A whole bunch of software has to be
  set up just right in order to get a network working. Server computers
  typically use a special network operating system (also known as a NOS)
  in order to function efficiently, and client computers need to have their
  network settings configured properly in order to access the network.
   One of the most important networking choices to make is which network
   operating system you’ll use on the network’s servers. That’s because
   much of the task of building a new network and managing an existing
   one is setting up and maintaining the network operating system on the
   servers.
12   What Is a Network?


        Why bother?
        If the truth be told, computer networks are a pain to set up. So, why bother?
        Because the benefits of having a network make the difficulty of setting one
        up worthwhile. You don’t have to be a Ph.D. to understand the benefits
        of networking. In fact, you learned everything you need to know about
        the benefits of networking in kindergarten. Networks are all about shar-
        ing. Specifically, networks are about sharing three things: information,
        resources, and applications.

         ✦ Sharing information: Networks allow users to share information in
           several different ways. The most common way of sharing information
           is to share individual files. For example, two or more people can work
           together on a single spreadsheet file or word-processing document. In
           most networks, a large hard drive on a central server computer is set up
           as a common storage area where users can store files to be shared with
           other users.
            In addition to sharing files, networks allow users to communicate with
            each other in various ways. For example, messaging applications let
            network users exchange messages with each other using an e-mail appli-
            cation such as Microsoft Outlook. Users can also hold online meetings
            over the network. In fact, with inexpensive video cameras and the right
            software, users can hold videoconferences over the network.
         ✦ Sharing resources: Certain computer resources, such as printers or hard
           drives, can be set up so that network users can share them. Sharing these
           resources can result in significant cost savings. For example, it’s cheaper
           to buy a single high-speed printer with advanced features such as collat-
           ing, stapling, and duplex printing that can be shared by an entire work-
           group than it is to buy separate printers for each user in the group.
            Hard drives can also be shared resources. In fact, providing users with
            access to a shared hard drive is the most common method of sharing
            files on a network. A computer whose main purpose in life is to host
            shared hard drives is called a file server.
            In actual practice, entire hard drives aren’t usually shared. Instead,
            individual folders on a networked hard drive are shared. This way, the
            network administrator can allow different network users to have access
            to different shared folders. For example, a company may set up shared
            folders for its sales department and accounting department. Then, sales
            personnel can access the sales department’s folder, and accounting per-
            sonnel can access the accounting department’s folder.
            You can share other resources on a network. For example, a network
            can be used to share an Internet connection. In the early days of the
            Internet, it was common for each user who required access to the
            Internet to have his or her own modem connection. Nowadays, it’s more
            common for the network to provide a shared, high-speed Internet con-
            nection that everyone on the network can access.
                                                   Of Clients and Servers         13

        ✦ Sharing applications: One of the most common reasons for network-                Book I
          ing in many businesses is so that several users can work together on            Chapter 1
          a single business application. For example, an accounting department
          may have accounting software that can be used from several comput-




                                                                                             Understanding
          ers at the same time. Or a sales-processing department may have an




                                                                                               Networks
          order-entry application that runs on several computers to handle a large
          volume of orders.



Of Clients and Servers
       The network computer that contains the hard drives, printers, and other
       resources that are shared with other network computers is called a server.
       This term comes up repeatedly, so you have to remember it. Write it on the
       back of your left hand.

       Any computer that’s not a server is called a client. You have to remember
       this term, too. Write it on the back of your right hand.

       Only two kinds of computers are on a network: servers and clients. Look at
       your left hand and then look at your right hand. Don’t wash your hands until
       you have these terms memorized.

       The distinction between servers and clients in a network would be some-
       what fun to study in a sociology class because it’s similar to the distinction
       between the haves and the have-nots in society:

        ✦ Usually, the most powerful and expensive computers in a network are
          the servers. This fact makes sense because every user on the network
          shares the server’s resources.
        ✦ The cheaper and less powerful computers in a network are the clients.
          Clients are the computers used by individual users for everyday work.
          Because clients’ resources don’t have to be shared, they don’t have to
          be as fancy.
        ✦ Most networks have more clients than servers. For example, a network
          with ten clients can probably get by with one server.
        ✦ In some networks, a clear line of segregation exists between servers and
          clients. In other words, a computer is either a server or a client, and not
          both. A server can’t become a client, nor can a client become a server.
        ✦ Other networks are more progressive, allowing any computer in the
          network to be a server and allowing any computer to be both server and
          client at the same time. The network illustrated in Figure 1-1, later in this
          chapter, is this type of network.
14   Dedicated Servers and Peers


Dedicated Servers and Peers
        In some networks, a server computer is a server computer and nothing else.
        This server computer is dedicated solely to the task of providing shared
        resources, such as hard drives and printers, to be accessed by the network
        client computers. Such a server is referred to as a dedicated server because
        it can perform no other tasks besides network services. A network that relies
        on dedicated servers is sometimes called a client/server network.

        Other networks take an alternative approach, enabling any computer on the
        network to function as both a client and a server. Thus, any computer can
        share its printers and hard drives with other computers on the network.
        And while a computer is working as a server, you can still use that same
        computer for other functions such as word processing. This type of network
        is called a peer-to-peer network because all the computers are thought of as
        peers, or equals.

        While you’re walking the dog tomorrow morning, ponder these points con-
        cerning the difference between dedicated server networks and peer-to-peer
        networks:

         ✦ Peer-to-peer networking has been built in to all versions of Windows
           since Windows 95. Thus, you don’t have to buy any additional software
           to turn your computer into a server. All you have to do is enable the
           Windows server features.
         ✦ The network server features that are built in to desktop versions of
           Windows (including Windows 7, Vista, and XP) aren’t very efficient
           because these versions of Windows were not designed primarily to be
           network servers. If you’re going to dedicate a computer to the task of
           being a full-time server, you should use a full-fledged network operating
           system, such as Windows Server 2008, instead.



Networks Big and Small
        Networks come in all sizes and shapes. In fact, it’s common to categorize
        networks based on the geographical size they cover, as described in the fol-
        lowing list:

         ✦ Local area networks: A local area network, or LAN, is a network in which
           computers are relatively close together, such as within the same office
           or building.
            Note that the term LAN doesn’t imply that the network is small. A LAN
            can, in fact, contain hundreds or even thousands of computers. What
            makes a network a LAN is that all those computers are located within
                                                     Network Topology          15

          close proximity to each other. Usually a LAN is contained within a single    Book I
          building, but a LAN can extend to several buildings on a campus —           Chapter 1
          provided the buildings are close to each other (typically within 300
          feet of each other, though greater distances are possible with special




                                                                                         Understanding
          equipment).




                                                                                           Networks
       ✦ Wide area networks: A wide area network, or WAN, is a network that
         spans a large geographic territory, such as an entire city or region, or
         even an entire country. WANs are typically used to connect two or more
         LANs that are relatively far apart. For example, a WAN may connect an
         office in San Francisco with an office in New York.
          Again, it’s the geographic distance, not the number of computers
          involved, that makes a network a WAN. If the office in San Francisco and
          the office in New York both have only one computer, the WAN will have
          a total of two computers but will span more than 3,000 miles.
       ✦ Metropolitan area networks: A metropolitan area network, or MAN,
         is a network that’s smaller than a typical WAN but larger than a LAN.
         Typically, a MAN connects two or more LANs that are within the same
         city but are far enough apart that the networks can’t be connected using
         a simple cable or wireless connection.



Network Topology
      The term network topology refers to the shape of how the computers and
      other network components are connected to each other. There are several dif-
      ferent types of network topologies, each with advantages and disadvantages.

      In the following discussion of network topologies, I use two important terms:

       ✦ Node: A node is a device that’s connected to the network. For your pur-
         poses here, a node is the same as a computer. Network topology deals
         with how the nodes of a network are connected to each other.
       ✦ Packet: A packet is a message that’s sent over the network from one
         node to another node. The packet includes the address of the node
         that sent the packet, the address of the node the packet is being sent
         to, and data.


      Bus topology
      The first type of network topology is called a bus, in which nodes are strung
      together in a line, as shown in Figure 1-1. The key to understanding how a
      bus topology works is to think of the entire network as a single cable, with
      each node “tapping” into the cable so it can listen in on the packets being
      sent over that cable. If you’re old enough to remember party lines, you get
      the idea.
16       Network Topology




Figure 1-1:
Bus
topology.



              In a bus topology, every node on the network can see every packet that’s
              sent on the cable. Each node looks at each packet to determine whether the
              packet is intended for it. If so, the node claims the packet. If not, the node
              ignores the packet. This way, each computer can respond to data sent to it
              and ignore data sent to other computers on the network.

              If the cable in a bus network breaks, the entire network is effectively dis-
              abled. Obviously the nodes on opposite sides of the break can’t continue to
              communicate with each other because data can’t span the gap created by
              the break. But even those nodes that are on the same side of the break will
              be unable to communicate with each other, because the open end of the
              cable left by the break disrupts the proper transmission of electrical signals.

              In the early days of Ethernet networking, bus topology was commonplace.
              Although bus topology has given way to star topology (see the next section)
              for most networks today, many networks today still have elements that rely
              on bus topology.


              Star topology
              In a star topology, each network node is connected to a central device called
              a hub or a switch, as shown in Figure 1-2. Star topologies are commonly used
              with LANs.

              If a cable in a star network breaks, only the node connected to that cable is
              isolated from the network. The other nodes can continue to operate without
              interruption — unless, of course, the node that’s isolated because of the
              break happens to be the file server.

              You should be aware of the somewhat technical distinction between a hub
              and a switch. Simply put, a hub doesn’t know anything about the computers
              that are connected to each of its ports. So when a computer connected to
              the hub sends a packet to a computer that’s connected to another port, the
              hub sends a duplicate copy of the packet to all its ports. In contrast, a switch
              knows which computer is connected to each of its ports. As a result, when
              a switch receives a packet intended for a particular computer, it sends the
              packet only to the port that the recipient is connected to.
                                                              Network Topology          17

                                                                                                 Book I
                                                                                                Chapter 1




                                                                                                   Understanding
                                                                                                     Networks
                                       Hub


Figure 1-2:
Star
topology.



              Strictly speaking, only networks that use switches have a true star topology.
              If the network uses a hub, the network topology has the physical appear-
              ance of a star, but is actually a bus. That’s because when a hub is used, each
              computer on the network sees all the packets sent over the network, just
              like in a bus topology. In a true star topology, as when a switch is used, each
              computer sees only those packets that were sent specifically to it, as well as
              packets that were specifically sent to all computers on the network (those
              types of packets are called broadcast packets).


              Expanding stars
              Physicists say that the universe is expanding, and network administrators
              know they’re right. A simple bus or star topology is suitable only for small
              networks, with a dozen or so computers. But small networks inevitably
              become large networks as more computers are added. For larger networks,
              it’s common to create more complicated topologies that combine stars and
              buses.

              For example, a bus can be used to connect several stars. In this case, two
              or more hubs or switches are connected to each other using a bus. Each
              of these hubs or switches is then the center of a star that connects two or
              more computers to the network. This type of arrangement is commonly used
              in buildings that have two or more distinct workgroups. The bus that con-
              nects the switches is sometimes called a backbone.

              Another way to expand a star topology is to use a technique called daisy-
              chaining. When you use daisy-chaining, a switch is connected to another
              switch as if it were one of the nodes on the star. Then, this second switch
              serves as the center of a second star.
18       Network Topology


              Ring topology
              A third type of network topology is called a ring, shown in Figure 1-3. In a
              ring topology, packets are sent around the circle from computer to com-
              puter. Each computer looks at each packet to decide whether the packet
              was intended for it. If not, the packet is passed on to the next computer in
              the ring.




Figure 1-3:
Ring
topology.



              Years ago, ring topologies were common in LANs, as two popular network-
              ing technologies used rings: ARCNET and Token Ring. ARCNET is still used
              for certain applications such as factory automation, but is rarely used in
              business networks. Token Ring is still a popular network technology for IBM
              midrange computers. Although plenty of Token Ring networks are still in
              existence, not many new networks use Token Ring any more.

              Ring topology was also used by FDDI, one of the first types of fiber-optic
              network connections. FDDI has given way to more efficient fiber-optic tech-
              niques, however. So ring networks have all but vanished from business
              networks.


              Mesh topology
              A fourth type of network topology, known as mesh, has multiple connec-
              tions between each of the nodes on the network, as shown in Figure 1-4. The
              advantage of a mesh topology is that if one cable breaks, the network can
              use an alternative route to deliver its packets.
                                                                    Network Topology         19

                                                                                                   Book I
                                         Router            Router                                 Chapter 1




                                                                                                     Understanding
                                                                                                       Networks
                               Router                                  Router
Figure 1-4:                                                                       Computer
Mesh              Computer
topology.                                         Router




              Mesh networks aren’t very practical in a LAN setting. For example, to net-
              work eight computers in a mesh topology, each computer would have
              to have seven network interface cards, and 28 cables would be required
              to connect each computer to the seven other computers in the network.
              Obviously, this scheme isn’t very scalable.

              However, mesh networks are common for metropolitan or wide area net-
              works. These networks use devices called routers to route packets from
              network to network. For reliability and performance reasons, routers are
              usually arranged in a way that provides multiple paths between any two
              nodes on the network in a meshlike arrangement.
20   Book I: Networking Basics
       Chapter 2: Understanding Network
       Protocols and Standards
       In This Chapter
       ✓ Deciphering the layers of the OSI reference model
       ✓ Understanding an Ethernet
       ✓ Getting the inside scoop on TCP/IP and IPX/SPX
       ✓ Finding out about other important protocols




       P     rotocols and standards are what make networks work together.
             Protocols make it possible for the various components of a network to
       communicate with each other. Standards also make it possible for network
       components manufactured by different companies to work together. This
       chapter introduces you to the protocols and standards that you’re most
       likely to encounter when building and maintaining a network.



Understanding Protocols
       A protocol is a set of rules that enables effective communications to occur.
       You encounter protocols every day. For example, when you pay for grocer-
       ies with a debit card, the clerk first tells you how much the groceries cost.
       You then swipe your debit card in the card reader, punch in your security
       code, indicate whether you want cash back, enter the amount of the cash
       back if you so indicated, then verify the total amount. You then cross your
       fingers behind your back and say a quiet prayer while the machine autho-
       rizes the purchase. Assuming the amount is authorized, the machine prints
       out your receipt.

       Here’s another example of an everyday protocol: making a phone call. You
       probably take most of the details of the phone-calling protocol for granted,
       but it’s pretty complicated if you think about it:

        ✦ When you pick up a phone, you must listen for a dial tone before dialing
          the number (unless you’re using a cell phone). If you don’t hear a dial
          tone, you know that either (1) someone else in your family is talking on
          the phone or (2) something is wrong with your phone.
22   Understanding Protocols


         ✦ When you hear the dial tone, you initiate the call by dialing the number
           of the party you want to reach. If the person you want to call is in the
           same area code as you, most of the time you simply dial that person’s
           seven-digit phone number. If the person is in a different area code, you
           dial a one, the three-digit area code, and the person’s seven-digit phone
           number.
         ✦ If you hear a series of long ringing tones, you wait until the other person
           answers the phone. If the phone rings a certain number of times with no
           answer, you hang up and try again later. If you hear a voice say, “Hello,”
           you begin a conversation with the other party. If the person on the
           other end of the phone has never heard of you, you say, “Sorry, wrong
           number,” hang up, and try again.
         ✦ If you hear a voice that rambles on about how they’re not home but they
           want to return your call, you wait for a beep and leave a message.
         ✦ If you hear a series of short tones, you know the other person is talking
           to someone else on the phone. So you hang up and try again later.
         ✦ If you hear a sequence of three tones that increase in pitch, followed by
           a recorded voice that says “We’re sorry . . .” you know that the number
           you dialed is invalid. Either you dialed the number incorrectly, or the
           number has been disconnected.

        I can go on and on, but I think you probably get the point. Exchanges such
        as using debit cards or making phone calls follow the same rules every time
        they happen.

        Computer networks depend upon many different types of protocols in order
        to work. These protocols are very rigidly defined, and for good reason.
        Network cards must know how to talk to other network cards in order to
        exchange information, operating systems must know how to talk to network
        cards in order to send and receive data on the network, and application pro-
        grams must know how to talk to operating systems in order to know how to
        retrieve a file from a network server.

        Protocols come in many different types. At the lowest level, protocols define
        exactly what type of electrical signal represents a one and what type of
        signal represents a zero. At the highest level, protocols allow a computer
        user in the United States to send an e-mail to another computer user in New
        Zealand. And in between are many other levels of protocols. You find out
        more about these levels of protocols (which are often called layers) in the
        section, “The Seven Layers of the OSI Reference Model,” later in this chapter.

        Various protocols tend to be used together in matched sets called protocol
        suites. The two most popular protocol suites for networking are TCP/IP and
        Ethernet. TCP/IP was originally developed for Unix networks and is the
                                             Understanding Standards             23

      protocol of the Internet and most local-area networks. Ethernet is a low-          Book I
      level protocol that spells out the electrical characteristics of the network      Chapter 2
      hardware used by most local-area networks. A third important protocol is




                                                                                        Network Protocols
      IPX/SPX, which is an alternative to TCP/IP that was originally developed for




                                                                                         Understanding
                                                                                         and Standards
      NetWare networks. In the early days of networking, IPX/SPX was widely
      used in local area networks, but TCP/IP is now the preferred protocol.



Understanding Standards
      A standard is an agreed-upon definition of a protocol. In the early days of
      computer networking, each computer manufacturer developed its own net-
      working protocols. As a result, you weren’t able to easily mix equipment
      from different manufacturers on a single network.

      Then along came standards to save the day. Standards are industry-wide
      protocol definitions that are not tied to a particular manufacturer. With stan-
      dard protocols, you can mix and match equipment from different vendors.
      As long as the equipment implements the standard protocols, it should be
      able to coexist on the same network.

      Many organizations are involved in setting standards for networking. The
      five most important organizations are

       ✦ American National Standards Institute (ANSI): The official standards
         organization in the United States. ANSI is pronounced AN-see.
       ✦ Institute of Electrical and Electronics Engineers (IEEE): An interna-
         tional organization that publishes several key networking standards —
         in particular, the official standard for the Ethernet networking system
         (known officially as IEEE 802.3). IEEE is pronounced eye-triple-E.
       ✦ International Organization for Standardization (ISO): A federation of
         more than 100 standards organizations from throughout the world. If
         I had studied French in high school, I’d probably understand why the
         acronym for International Organization for Standardization is ISO, and
         not IOS.
       ✦ Internet Engineering Task Force (IETF): The organization responsible
         for the protocols that drive the Internet.
       ✦ World Wide Web Consortium (W3C): An international organization that
         handles the development of standards for the World Wide Web.

      Table 2-1 lists the Web sites for each of these standards organizations.
24   The Seven Layers of the OSI Reference Model



          Table 2-1             Web Sites for Major Standards Organizations
          Organization                                                Web Site
          ANSI (American National Standards Institute)                www.ansi.org
          IEEE (Institute of Electrical and Electronic Engineers)     www.ieee.org
          ISO (International Organization for Standardization)        www.iso.org
          IETF (Internet Engineering Task Force)                      www.ietf.org
          W3C (World Wide Web Consortium)                             www.w3c.org




The Seven Layers of the OSI Reference Model
        OSI sounds like the name of a top-secret government agency you hear about
        only in Tom Clancy novels. What it really stands for in the networking world
        is Open Systems Interconnection, as in the Open Systems Interconnection
        Reference Model, affectionately known as the OSI model.

        The OSI model breaks the various aspects of a computer network into seven
        distinct layers. These layers are kind of like the layers of an onion: Each suc-
        cessive layer envelops the layer beneath it, hiding its details from the levels
        above. The OSI model is also like an onion in that if you start to peel it apart
        to have a look inside, you’re bound to shed a few tears.

        The OSI model is not a networking standard in the same sense that Ethernet
        and TCP/IP are networking standards. Rather, the OSI model is a framework
        into which the various networking standards can fit. The OSI model specifies
        what aspects of a network’s operation can be addressed by various network
        standards. So, in a sense, the OSI model is sort of a standard of standards.

        Table 2-2 summarizes the seven layers of the OSI model.



          Table 2-2                  The Seven Layers of the OSI Model
          Layer      Name                Description
          1          Physical            Governs the layout of cables and devices such as
                                         repeaters and hubs.
          2          Data Link           Provides MAC addresses to uniquely identify net-
                                         work nodes and a means for data to be sent over the
                                         Physical layer in the form of packets. Bridges and
                                         switches are layer 2 devices.
          3          Network             Handles routing of data across network segments.
                 The Seven Layers of the OSI Reference Model                    25

  Layer     Name             Description                                              Book I
                                                                                     Chapter 2
  4         Transport        Provides for reliable delivery of packets.




                                                                                     Network Protocols
  5         Session          Establishes sessions between network applications.




                                                                                      Understanding
                                                                                      and Standards
  6         Presentation     Converts data so that systems that use different data
                             formats can exchange information.
  7         Application      Allows applications to request network services.


The first three layers are sometimes called the lower layers. They deal with
the mechanics of how information is sent from one computer to another
over a network. Layers 4 through 7 are sometimes called the upper layers.
They deal with how application software can relate to the network through
application programming interfaces.

The following sections describe each of these layers in greater detail.

The seven layers of the OSI model are a somewhat idealized view of how
networking protocols should work. In the real world, actual networking
protocols don’t follow the OSI model to the letter. The real world is always
messier than we’d like. Still, the OSI model provides a convenient — if not
completely accurate — conceptual picture of how networking works.


The Physical Layer
The bottom layer of the OSI model is the Physical layer. It addresses the
physical characteristics of the network, such as the types of cables used to
connect devices, the types of connectors used, how long the cables can be,
and so on. For example, the Ethernet standard for 10BaseT cable specifies
the electrical characteristics of the twisted-pair cables, the size and shape of
the connectors, the maximum length of the cables, and so on. The star, bus,
ring, and mesh network topologies described in Book I, Chapter 1 apply to
the Physical layer.

Another aspect of the Physical layer is the electrical characteristics of the
signals used to transmit data over the cables from one network node to
another. The Physical layer doesn’t define any meaning to those signals
other than the basic binary values of zero and one. The higher levels of
the OSI model must assign meanings to the bits that are transmitted at the
Physical layer.

One type of Physical layer device commonly used in networks is a repeater.
A repeater is used to regenerate the signal whenever you need to exceed
the cable length allowed by the Physical layer standard. 10BaseT hubs are
also Physical layer devices. Technically, they’re known as multiport repeat-
ers because the purpose of a hub is to regenerate every packet received on
26       The Seven Layers of the OSI Reference Model


              any port on all of the hub’s other ports. Repeaters and hubs don’t examine
              the contents of the packets that they regenerate. If they did, they would be
              working at the Data Link layer, and not at the Physical layer.

              The network adapter (also called a network interface card or NIC) that’s
              installed in each computer on the network is a Physical layer device. You
              can display information about the network adapter (or adapters) installed
              in a Windows computer by displaying the adapter’s Properties dialog box,
              as shown in Figure 2-1. To access this dialog box in Windows 7 or Vista,
              open the Control Panel, choose Network and Internet, choose View Network
              Status and Tasks, and choose Change Adapter Settings. Then, right-click
              the Local Area Connection icon and choose Properties from the menu that
              appears.




Figure 2-1:
The
Properties
dialog
box for a
network
adapter.




              The Data Link Layer
              The Data Link layer is the lowest layer at which meaning is assigned to the
              bits that are transmitted over the network. Data link protocols address
              things such as the size of each packet of data to be sent, a means of address-
              ing each packet so that it’s delivered to the intended recipient, and a way to
              ensure that two or more nodes don’t try to transmit data on the network at
              the same time.

              The Data Link layer also provides basic error detection and correction to
              ensure that the data sent is the same as the data received. If an uncorrect-
              able error occurs, the data link standard must specify how the node is to be
              informed of the error so that it can retransmit the data.
                                 The Seven Layers of the OSI Reference Model             27

                At the Data Link layer, each device on the network has an address known as       Book I
                the Media Access Control address, or MAC address. This address is actually      Chapter 2
                hard-wired into every network device by the manufacturer. MAC addresses




                                                                                                Network Protocols
                are unique; no two network devices made by any manufacturer anywhere in




                                                                                                 Understanding
                                                                                                 and Standards
                the world can have the same MAC address.

                You can see the MAC address for a computer’s network adapter by opening
                a command window and running the ipconfig /all command, as shown
                in Figure 2-2. In this example, the MAC address of the network card is A4-BA-
                DB-01-99-E8. (The ipconfig command refers to the MAC address as the
                physical address.)




Figure 2-2:
Using the
ipconfig /all
command
to display
the MAC
address of
a network
adapter.



                One of the most import functions of the Data Link layer is to provide a way
                for packets to be sent safely over the physical media without interference
                from other nodes attempting to send packets at the same time. The two
                most popular ways to do this are CSMA/CD and token passing. Ethernet net-
                works use CSMA/CD, and Token Ring networks use token passing.

                Two types of Data Link layer devices are commonly used on networks: bridges
                and switches. A bridge is an intelligent repeater that is aware of the MAC
                addresses of the nodes on either side of the bridge and can forward packets
                accordingly. A switch is an intelligent hub that examines the MAC address of
                arriving packets in order to determine which port to forward the packet to.

                An important function of the Data Link layer is to make sure that two com-
                puters don’t try to send packets over the network at the same time. If they
                do, the signals will collide with each other, and the transmission will be
                garbled. Ethernet accomplishes this feat by using a technique called CSMA/
                CD, which stands for carrier sense multiple access with collision detection.
28   The Seven Layers of the OSI Reference Model


        This phrase is a mouthful, but if you take it apart piece by piece, you’ll get
        an idea of how it works.

        Carrier sense means that whenever a device wants to send a packet over the
        network media, it first listens to the network media to see whether anyone
        else is already sending a packet. If it doesn’t hear any other signals on
        the media, the computer assumes that the network is free, so it sends the
        packet.

        Multiple access means that nothing prevents two or more devices from
        trying to send a message at the same time. Sure, each device listens before
        sending. However, suppose that two devices listen, hear nothing, and then
        proceed to send their packets at the same time? Picture what happens
        when you and someone else arrive at a four-way stop sign at the same time.
        You wave the other driver on, he or she waves you on, you wave, he or she
        waves, you both wave, and then you both go at the same time.

        Collision detection means that after a device sends a packet, it listens care-
        fully to see whether the packet crashes into another packet. This is kind of
        like listening for the screeching of brakes at the four-way stop. If the device
        hears the screeching of brakes, it waits a random period of time and then
        tries to send the packet again. Because the delay is random, two packets
        that collide are sent again after different delay periods, so a second collision
        is unlikely.

        CSMA/CD works pretty well for smaller networks. After a network hits about
        30 computers, however, packets start to collide like crazy, and the network
        slows to a crawl. When that happens, the network should be divided into
        two or more separate sections that are sometimes called collision domains.


        The Network Layer
        The Network layer handles the task of routing network messages from one
        computer to another. The two most popular layer 3 protocols are IP (which
        is usually paired with TCP) and IPX (normally paired with SPX for use with
        Novell and Windows networks).

        Network layer protocols provide two important functions: logical addressing
        and routing. The following sections describe these functions.


        Logical addressing
        As you know, every network device has a physical address called a MAC
        address, which is assigned to the device at the factory. When you buy a
        network interface card to install into a computer, the MAC address of that
        card is fixed and can’t be changed. But what if you want to use some other
                               The Seven Layers of the OSI Reference Model            29

              addressing scheme to refer to the computers and other devices on your            Book I
              network? This is where the concept of logical addressing comes in; a logi-      Chapter 2
              cal address lets you access a network device by using an address that you




                                                                                              Network Protocols
              assign.




                                                                                               Understanding
                                                                                               and Standards
              Logical addresses are created and used by Network layer protocols such as
              IP or IPX. The Network layer protocol translates logical addresses to MAC
              addresses. For example, if you use IP as the Network layer protocol, devices
              on the network are assigned IP addresses such as 207.120.67.30. Because
              the IP protocol must use a Data Link layer protocol to actually send packets
              to devices, IP must know how to translate the IP address of a device to the
              device’s MAC address.

              You can use the ipconfig command shown earlier in Figure 2-2 to see the
              IP address of your computer. The IP address shown in the figure is
              192.168.1.100. Another way to display this information is to use the System
              Information command, found on the Start menu under Start➪All Programs➪
              Accessories➪System Tools➪System Information. The IP address is high-
              lighted in Figure 2-3. Notice that the System Information program displays a
              lot of other useful information about the network besides the IP address. For
              example, you can also see the MAC address, what protocols are being used,
              and other information.




Figure 2-3:
Displaying
network
information
using the
System
Information
program.
30   The Seven Layers of the OSI Reference Model


        Although the exact format of logical addresses varies depending on the pro-
        tocol being used, most protocols divide the logical address into two parts:
        a network address and a device address. The network address identifies
        which network the device resides on, and the device address then identi-
        fies the device on that network. For example, in a typical IP address, such
        as 192.168.1.102, the network address is 192.168.1, and the device address
        (called a host address in IP) is 102.

        Similarly, IPX addresses consist of two parts: a network address and a
        node address. In an IPX address, the node address is the same as the MAC
        address. As a result, IPX doesn’t have to translate between layer 3 and layer
        2 addresses.


        Routing
        Routing comes into play when a computer on one network needs to send
        a packet to a computer on another network. In this case, a device called
        a router is used to forward the packet to the destination network. In some
        cases, a packet may actually have to travel through several intermediate net-
        works in order to reach its final destination network. You can find out more
        about routers in Book I, Chapter 3.

        An important feature of routers is that you can use them to connect net-
        works that use different layer 2 protocols. For example, a router can be used
        to send a packet from an Ethernet to a Token Ring network. As long as both
        networks support the same layer 3 protocol, it doesn’t matter whether their
        layer 1 and layer 2 protocols are different.

        A protocol is considered routable if it uses addresses that include a net-
        work part and a host part. Any protocol that uses physical addresses isn’t
        routable because physical addresses don’t indicate to which network a
        device belongs.


        The Transport Layer
        The Transport layer is the layer where you’ll find two of the most well-known
        networking protocols: TCP (normally paired with IP) and SPX (normally
        paired with IPX). As its name implies, the Transport layer is concerned with
        the transportation of information from one computer to another.

        The main purpose of the Transport layer is to ensure that packets are
        transported reliably and without errors. The Transport layer does this task
        by establishing connections between network devices, acknowledging the
        receipt of packets, and resending packets that aren’t received or are cor-
        rupted when they arrive.
                                The Seven Layers of the OSI Reference Model            31

              In many cases, the Transport layer protocol divides large messages into          Book I
              smaller packets that can be sent over the network efficiently. The Transport    Chapter 2
              layer protocol reassembles the message on the receiving end, making sure




                                                                                              Network Protocols
              that all the packets that comprise a single transmission are received so that




                                                                                               Understanding
                                                                                               and Standards
              no data is lost.

              For some applications, speed and efficiency are more important than reli-
              ability. In such cases, a connectionless protocol can be used. A connection-
              less protocol doesn’t go to the trouble of establishing a connection before
              sending a packet. Instead, it simply sends the packet. TCP is a connection-
              oriented Transport layer protocol. The connectionless protocol that works
              alongside TCP is called UDP.

              In Windows XP or Vista, you can view information about the status of TCP
              and UDP connections by running the Netstat command from a command
              window, as Figure 2-4 shows. In the figure, you can see that several TCP con-
              nections are established.




Figure 2-4:
Using the
Netstat
command.



              In fact, you can use the command Netstat /N to see the numeric network
              addresses instead of the names. With the /N switch, the output in Figure 2-4
              would look like this:

              Active Connections

                Proto   Local Address         Foreign Address     State
                TCP     127.0.0.1:2869        127.0.0.1:54170     ESTABLISHED
                TCP     127.0.0.1:5357        127.0.0.1:54172     TIME_WAIT
                TCP     127.0.0.1:27015       127.0.0.1:49301     ESTABLISHED
                TCP     127.0.0.1:49301       127.0.0.1:27015     ESTABLISHED
                TCP     127.0.0.1:54170       127.0.0.1:2869      ESTABLISHED
                TCP     192.168.1.100:49300   192.168.1.101:445   ESTABLISHED
32   The Seven Layers of the OSI Reference Model


        TCP is a connection-oriented Transport layer protocol. UDP is a connection-
        less Transport layer protocol.


        The Session Layer
        The Session layer establishes conversations known as sessions between net-
        worked devices. A session is an exchange of connection-oriented transmis-
        sions between two network devices. Each of these transmissions is handled
        by the Transport layer protocol. The session itself is managed by the
        Session layer protocol.

        A single session can include many exchanges of data between the two com-
        puters involved in the session. After a session between two computers has
        been established, it is maintained until the computers agree to terminate the
        session.

        The Session layer allows three types of transmission modes:

         ✦ Simplex: In this mode, data flows in only one direction.
         ✦ Half-duplex: In this mode, data flows in both directions, but only in one
           direction at a time.
         ✦ Full-duplex: In this mode, data flows in both directions at the same time.

        In actual practice, the distinctions in the Session, Presentation, and
        Application layers are often blurred, and some commonly used protocols
        actually span all three layers. For example, SMB — the protocol that is the
        basis of file sharing in Windows networks — functions at all three layers.


        The Presentation Layer
        The Presentation layer is responsible for how data is represented to appli-
        cations. Most computers — including Windows, Unix, and Macintosh
        computers — use the American Standard Code for Information Interchange
        (ASCII) to represent data. However, some computers (such as IBM main-
        frame computers) use a different code, known as Extended Binary Coded
        Decimal Interchange Code (EBCDIC). ASCII and EBCDIC aren’t compatible
        with each other. To exchange information between a mainframe computer
        and a Windows computer, the Presentation layer must convert the data
        from ASCII to EBCDIC and vice versa.

        Besides simply converting data from one code to another, the Presentation
        layer can also apply sophisticated compression techniques so that fewer
        bytes of data are required to represent the information when it’s sent over
        the network. At the other end of the transmission, the Presentation layer
        then uncompresses the data.
                                Following a Packet through the Layers           33

       The Presentation layer can also scramble the data before it is transmitted        Book I
       and unscramble it at the other end by using a sophisticated encryption tech-     Chapter 2
       nique that even Sherlock Holmes would have trouble breaking.




                                                                                        Network Protocols
                                                                                         Understanding
                                                                                         and Standards
       The Application Layer
       The highest layer of the OSI model, the Application layer, deals with the
       techniques that application programs use to communicate with the network.
       The name of this layer is a little confusing. Application programs such as
       Microsoft Office or QuickBooks aren’t a part of the Application layer. Rather,
       the Application layer represents the programming interfaces that applica-
       tion programs such as Microsoft Office or QuickBooks use to request net-
       work services.

       Some of the better-known Application layer protocols are

        ✦ DNS (Domain Name System) for resolving Internet domain names.
        ✦ FTP (File Transfer Protocol) for file transfers.
        ✦ SMTP (Simple Mail Transfer Protocol) for e-mail.
        ✦ SMB (Server Message Block) for file sharing in Windows networks.
        ✦ NFS (Network File System) for file sharing in Unix networks.
        ✦ Telnet for terminal emulation.



Following a Packet through the Layers
       Figure 2-5 shows how a packet of information flows through the seven layers
       as it travels from one computer to another on the network. The data begins
       its journey when an end-user application sends data to another network
       computer. The data enters the network through an Application layer inter-
       face, such as SMB. The data then works its way down through the protocol
       stack. Along the way, the protocol at each layer manipulates the data by
       adding header information, converting the data into different formats, com-
       bining packets to form larger packets, and so on. When the data reaches the
       Physical layer protocol, it’s actually placed on the network media (in other
       words, the cable) and sent to the receiving computer.

       When the receiving computer receives the data, the data works its way up
       through the protocol stack. Then, the protocol at each layer reverses the
       processing that was done by the corresponding layer on the sending com-
       puter. Headers are removed, data is converted back to its original format,
       packets that were split into smaller packets are recombined into larger mes-
       sages, and so on. When the packet reaches the Application layer protocol,
       it’s delivered to an application that can process the data.
34       The Ethernet Protocol



                    Data sent by user                   Data received by user


                      Application          Layer 7           Application


                      Presentation         Layer 6          Presentation


                        Session            Layer 5            Session


                       Transport           Layer 4           Transport


                        Network            Layer 3            Network


                       Data Link           Layer 2            Data Link
Figure 2-5:
How data
travels                 Physical           Layer 1            Physical
through
the seven
layers.                                 Network Media




The Ethernet Protocol
              As you know, the first two layers of the OSI model deal with the physical
              structure of the network and the means by which network devices can send
              information from one device on a network to another. By far, the most popu-
              lar set of protocols for the Physical and Data Link layers is Ethernet.

              Ethernet has been around in various forms since the early 1970s. (For a
              brief history of Ethernet, see the sidebar, “Ethernet folklore and mythology,”
              later in this chapter.) The current incarnation of Ethernet is defined by the
              IEEE standard known as 802.3. Various flavors of Ethernet operate at differ-
              ent speeds and use different types of media. However, all the versions of
              Ethernet are compatible with each other, so you can mix and match them on
              the same network by using devices such as bridges, hubs, and switches to
              link network segments that use different types of media.
                                                                The Ethernet Protocol                     35

              The actual transmission speed of Ethernet is measured in millions of bits per                     Book I
              second, or Mbps. Ethernet comes in three different speed versions: 10 Mbps,                      Chapter 2
              known as Standard Ethernet; 100 Mbps, known as Fast Ethernet; and 1,000




                                                                                                               Network Protocols
              Mbps, known as Gigabit Ethernet. Keep in mind, however, that network trans-




                                                                                                                Understanding
                                                                                                                and Standards
              mission speed refers to the maximum speed that can be achieved over the
              network under ideal conditions. In reality, the actual throughput of an
              Ethernet network rarely reaches this maximum speed.

              Ethernet operates at the first two layers of the OSI model — the Physical
              and the Data Link layers. However, Ethernet divides the Data Link layer into
              two separate layers known as the Logical Link Control (LLC) layer and the
              Medium Access Control (MAC) layer. Figure 2-6 shows how the various ele-
              ments of Ethernet match up to the OSI model.


                       OSI                                        Ethernet

                                                          Logical Link Control (LLC)
                  Data Link Layer
                                                    Medium Access Control (MAC)


                                      Standard Ethernet         Fast Ethernet          Gigabit Ethernet
Figure 2-6:                                10Base5               100BaseTX                1000BaseT
Ethernet          Physical Layer           10Base2               100BaseT4               1000BaseLX
and the OSI                                10BaseT               100BaseFX
model.                                    10BaseFX



              The following sections describe Standard Ethernet, Fast Ethernet, and
              Gigabit Ethernet in more detail.


              Standard Ethernet
              Standard Ethernet is the original Ethernet. It runs at 10 Mbps, which was
              considered fast in the 1970s but is pretty slow by today’s standards.
              Although there is still plenty of existing Standard Ethernet in use, it is con-
              sidered obsolete and should be replaced by Gigabit Ethernet as soon as
              possible.

              Standard Ethernet comes in four incarnations, depending on the type of
              cable used to string the network together:
36   The Ethernet Protocol


         ✦ 10Base5: The original Ethernet cable was thick (about as thick as
           your thumb), heavy, and difficult to work with. It’s seen today only in
           museums.
         ✦ 10Base2: This thinner type of coaxial cable (it resembles television
           cable) became popular in the 1980s and lingered into the early 1990s.
           Plenty of 10Base2 cable is still in use, but it’s rarely installed in new net-
           works. 10Base2 (like 10Base5) uses a bus topology, so wiring a 10Base2
           network involves running cable from one computer to the next until all
           the computers are connected in a segment.
         ✦ 10BaseT: Unshielded twisted-pair cable (also known as UTP) became
           popular in the 1990s because it’s easier to install, lighter, and more
           reliable, and it offers more flexibility in how networks are designed.
           10BaseT networks use a star topology with hubs at the center of
           each star. Although the maximum length of 10BaseT cable is only 100
           meters, hubs can be chained together to extend networks well beyond
           the 100-meter limit.
            10BaseT cable has four pairs of wires that are twisted together through-
            out the entire span of the cable. However, 10BaseT uses only two of
            these wire pairs, so the unused pairs are spares.
         ✦ 10BaseFL: Fiber-optic cables were originally supported at 10 Mbps by
           the 10BaseFL standard. However, because faster fiber-optic versions of
           Ethernet now exist, 10BaseFL is rarely used.


        Fast Ethernet
        Fast Ethernet refers to Ethernet that runs at 100 Mbps, which is ten times
        the speed of Standard Ethernet. The following are the three varieties of Fast
        Ethernet:

         ✦ 100BaseT4: The 100BaseT4 protocol allows transmission speeds of
           100 Mbps over the same UTP cable as 10BaseT networks. To do this, it
           uses all four pairs of wire in the cable. 100BaseT4 simplifies the task of
           upgrading an existing 10BaseT network to 100 Mbps.
         ✦ 100BaseTX: The most commonly used standard for office networks
           today is 100BaseTX, which transmits at 100 Mbps over just two pairs of
           a higher grade of UTP cable than the cable used by 10BaseT. The higher-
           grade cable is referred to as Category 5. Most new networks are wired
           with Category 5 or better cable.
         ✦ 100BaseFX: The fiber-optic version of Ethernet running at 100 Mbps
           is called 100BaseFX. Because fiber-optic cable is expensive and tricky
           to install, it isn’t used much for individual computers in a network.
           However, it’s commonly used as a network backbone. For example, a
           fiber backbone is often used to connect individual workgroup hubs to
           routers and servers.
                                                            The TCP/IP Protocol Suite              37

                                                                                                         Book I
                                                                                                        Chapter 2
                     Ethernet folklore and mythology




                                                                                                        Network Protocols
  If you’re a history buff, you may be interested in   interface complete with icons, windows, and




                                                                                                         Understanding
                                                                                                         and Standards
  the story of how Ethernet came to be so popu-        menus, and the world’s first laser printer.)
  lar. Here’s how it happened: The original idea
                                                       In 1979, Xerox began working with Intel and
  for the Ethernet was hatched in the mind of a
                                                       DEC (a once popular computer company) to
  graduate computer science student at Harvard
                                                       make Ethernet an industry standard networking
  University named Robert Metcalfe. Looking for
                                                       product. Along the way, they enlisted the help
  a thesis idea in 1970, he refined a networking
                                                       of the IEEE, which formed committee number
  technique that was used in Hawaii, called the
                                                       802.3 and began the process of standardizing
  AlohaNet (it was actually a wireless network),
                                                       Ethernet in 1981. The 802.3 committee released
  and developed a technique that would enable
                                                       the first official Ethernet standard in 1983.
  a network to efficiently use as much as 90 per-
  cent of its capacity. By 1973, he had his first      Meanwhile, Bob Metcalfe left Xerox, turned
  Ethernet network up and running at the famous        down a job offer from Steve Jobs to work at
  Xerox Palo Alto Research Center (PARC). Bob          Apple computers, and started a company
  dubbed his network “Ethernet” in honor of            called the Computer, Communication, and
  the thick network cable, which he called “the        Compatibility Corporation — now known as
  ether.” (Xerox PARC was busy in 1973. In addi-       3Com. 3Com has since become one of the larg-
  tion to Ethernet, PARC developed the first           est manufacturers of Ethernet equipment in the
  personal computer that used a graphical user         world.




             Gigabit Ethernet
             Gigabit Ethernet is Ethernet running at a whopping 1,000 Mbps, which is 100
             times faster than the original 10 Mbps Ethernet. Gigabit Ethernet was once
             considerably more expensive than Fast Ethernet, so it was used only when
             the improved performance justified the extra cost. However, today Gigabit
             Ethernet is the standard for nearly all desktop and laptop PCs.

             Gigabit Ethernet comes in two flavors:

              ✦ 1000BaseT: Gigabit Ethernet can run on Category 5 UTP cable, but
                higher grades such as Category 5e or Category 6 are preferred because
                they’re more reliable.
              ✦ 1000BaseLX: Several varieties of fiber cable are used with Gigabit
                Ethernet, but the most popular is called 1000BaseLX.



The TCP/IP Protocol Suite
             TCP/IP, the protocol on which the Internet is built, is actually not a single
             protocol but rather an entire suite of related protocols. TCP is even older
             than Ethernet. It was first conceived in 1969 by the Department of Defense.
38       The TCP/IP Protocol Suite


              For more on the history of TCP/IP, see the sidebar, “The fascinating story of
              TCP/IP,” later in this chapter. Currently, the Internet Engineering Task Force,
              or IETF, manages the TCP/IP protocol suite.

              The TCP/IP suite is based on a four-layer model of networking that is simi-
              lar to the seven-layer OSI model. Figure 2-7 shows how the TCP/IP model
              matches up with the OSI model and where some of the key TCP/IP protocols
              fit into the model. As you can see, the lowest layer of the model, the Network
              Interface layer, corresponds to the OSI model’s Physical and Data Link
              layers. TCP/IP can run over a wide variety of Network Interface layer proto-
              cols, including Ethernet, as well as other protocols, such as Token Ring and
              FDDI (an older standard for fiber-optic networks).


                    OSI Layers       TCP/IP Layers                         TCP/IP Protocols
                Application Layer
               Presentation Layer   Application Layer   HTTP         FTP        Telnet        SMTP      DNS
                   Session Layer

                 Transport Layer     Transport Layer            TCP                             UDP


Figure 2-7:        Network Layer     Network Layer                                IP
TCP/IP and
the OSI          Data Link Layer    Network Interface                                          Other Link-Layer
                                                          Ethernet           Token Ring
model.             Physical Layer        Layer                                                    Protocols




              The Application layer of the TCP/IP model corresponds to the upper three
              layers of the OSI model — that is, the Session, Presentation, and Application
              layers. Many protocols can be used at this level. A few of the most popular
              are HTTP, FTP, Telnet, SMTP, DNS, and SNMP.

              You can find out about many of the details of these and other TCP/IP proto-
              cols in Book IV. In the following sections, I just want to point out a few more
              details of the three most important protocols in the TCP/IP suite: IP, TCP,
              and UDP.


              IP
              IP, which stands for Internet Protocol, is a Network layer protocol that is
              responsible for delivering packets to network devices. The IP protocol uses
              logical IP addresses to refer to individual devices rather than physical (MAC)
              addresses. A protocol called ARP (for Address Resolution Protocol) handles
              the task of converting IP addresses to MAC addresses.
                                                       The TCP/IP Protocol Suite               39

                                                                                                      Book I
                                                                                                     Chapter 2




                                                                                                     Network Protocols
                                   10Base what?




                                                                                                      Understanding
                                                                                                      and Standards
The names of Ethernet cable standards resem-         which can carry more than one signal at a
ble the audible signals a quarterback might          time but is more difficult to implement. At
shout at the line of scrimmage. In reality, the      one time, broadband incarnations of the
cable designations consist of three parts:           802.x networking standards existed, but
                                                     they have all but fizzled due to lack of use.
✓ The first number is the speed of the net-
    work in Mbps. So 10BaseT is for 10 Mbps       ✓ The tail end of the designation indicates the
    networks (Standard Ethernet), 100BaseTX          cable type. For coaxial cables, a number is
    is for 100 Mbps networks (Fast Ethernet),        used that roughly indicates the maximum
    and 1000BaseT is for 1,000 Mbps networks         length of the cable in hundreds of meters.
    (Gigabit Ethernet).                              10Base5 cables can run up to 500 meters.
                                                     10Base2 cables can run up to 185 meters.
✓ The word Base indicates the type of net-
                                                     (The IEEE rounded 185 up to 200 to come up
    work transmission that the cable uses.
                                                     with the name 10Base2.) If the designation
    Base is short for baseband. Baseband
                                                     ends with a T, twisted-pair cable is used.
    transmissions carry one signal at a time
                                                     Other letters are used for other types of
    and are relatively simple to implement.
                                                     cables.
    The alternative to baseband is broadband,



          Because IP addresses consist of a network part and a host part, IP is a
          routable protocol. As a result, IP can forward a packet to another network if
          the host is not on the current network. (The ability to route packets across
          networks is where IP gets its name. An internet is a series of two or more
          connected TCP/IP networks that can be reached by routing.)


          TCP
          TCP, which stands for Transmission Control Protocol, is a connection-ori-
          ented Transport layer protocol. TCP lets a device reliably send a packet to
          another device on the same network or on a different network. TCP ensures
          that each packet is delivered if at all possible. It does so by establishing
          a connection with the receiving device and then sending the packets. If a
          packet doesn’t arrive, TCP resends the packet. The connection is closed
          only after the packet has been successfully delivered or an unrecoverable
          error condition has occurred.

          One key aspect of TCP is that it’s always used for one-to-one communica-
          tions. In other words, TCP allows a single network device to exchange data
          with another single network device. TCP isn’t used to broadcast messages
          to multiple network recipients. Instead, the User Datagram Protocol (UDP) is
          used for that purpose.
40         The TCP/IP Protocol Suite




                         The fascinating story of TCP/IP
     Some people are fascinated by history. They          Fortunately, the designers of IP realized that it
     subscribe to cable TV just to get the History        wouldn’t be too long before other networks
     Channel. If you’re one of those history buffs,       wanted to join in the fun, so they designed IP to
     you may be interested in the following chron-        allow for more than two networks. In fact, their
     icle of TCP/IP’s humble origins. (For maximum        ingenious design allowed for tens of thousands
     effect, play some melancholy violin music in         of networks to communicate via IP.
     the background as you read the rest of this
                                                          The decision was a fortuitous one, as the
     sidebar.)
                                                          Internet quickly began to grow. By the mid-
     In the summer of 1969, the four mop-topped           1980s, the original ARPANET reached its limits.
     singers from Liverpool were breaking up. The         Just in time, the National Science Foundation
     war in Vietnam was escalating. Astronauts            (NSF) decided to get into the game. NSF had
     Neil Armstrong and Buzz Aldrin walked on the         built a network called NSFNET to link its huge
     moon. And the Department of Defense built a          supercomputers. NSFNET replaced ARPANET
     computer network called ARPANET to link its          as the new background for the Internet.
     defense installations with several major uni-        Around that time, such magazines as Time and
     versities throughout the United States.              Newsweek began writing articles about this
                                                          new phenomenon called the Internet, and the
     By the early 1970s, ARPANET was becoming
                                                          Net (as it became nicknamed) began to grow
     difficult to manage. So it was split into two net-
                                                          like wildfire. Soon NSFNET couldn’t keep up
     works: one for military use, called MILNET, and
                                                          with the growth, so several private commer-
     the other for nonmilitary use. The nonmilitary
                                                          cial networks took over management of the
     network retained the name ARPANET. To link
                                                          Internet backbone. The Internet has grown at
     MILNET with ARPANET, a new method of con-
                                                          a dizzying rate ever since, and nobody knows
     necting networks, called Internet Protocol or
                                                          how long this frenetic growth rate will con-
     just IP for short, was invented.
                                                          tinue. One thing is sure: TCP/IP is now the most
     The whole purpose of IP was to enable these          popular networking protocol in the world.
     two networks to communicate with each other.



                Many well-known Application layer protocols rely on TCP. For example,
                when a user running a Web browser requests a page, the browser uses
                HTTP to send a request via TCP to the Web server. When the Web server
                receives the request, it uses HTTP to send the requested Web page back to
                the browser, again via TCP. Other Application layer protocols that use TCP
                include Telnet (for terminal emulation), FTP (for file exchange), and SMTP
                (for e-mail).


                UDP
                The User Datagram Protocol (or UDP) is a connectionless Transport layer
                protocol that is used when the overhead of a connection isn’t required.
                After UDP has placed a packet on the network (via the IP protocol), it forgets
                                 Other Protocols Worth Knowing About              41

       about it. UDP doesn’t guarantee that the packet actually arrives at its desti-     Book I
       nation. Most applications that use UDP simply wait for any replies expected       Chapter 2
       as a result of packets sent via UDP. If a reply doesn’t arrive within a certain




                                                                                         Network Protocols
       period of time, the application either sends the packet again or gives up.




                                                                                          Understanding
                                                                                          and Standards
       Probably the best-known Application layer protocol that uses UDP is DNS,
       the Domain Name System. When an application needs to access a domain
       name such as www.wiley.com, DNS sends a UDP packet to a DNS server
       to look up the domain. When the server finds the domain, it returns the
       domain’s IP address in another UDP packet. (Actually, the process is much
       more complicated than that. For a more detailed explanation, see Book IV,
       Chapter 4.)



Other Protocols Worth Knowing About
       Other networks besides Ethernet, TCP/IP, and IPX/SPX are worth knowing
       about:

        ✦ NetBIOS: Short for Network Basic Input/Output System, this is the basic
          application-programming interface for network services on Windows
          computers. It’s installed automatically when you install TCP/IP, but
          doesn’t show up as a separate protocol when you view the network con-
          nection properties. (Refer to Figure 2-1.) NetBIOS is a Session layer pro-
          tocol that can work with Transport layer protocols such as TCP, SPX, or
          NetBEUI.
        ✦ NetBEUI: Short for Network BIOS Extended User Interface, this is a
          Transport layer protocol that was designed for early IBM and Microsoft
          networks. NetBEUI is now considered obsolete.
        ✦ IPX/SPX: A protocol suite that was made popular in the 1980s by Novell
          for use with their NetWare servers. TCP/IP has become so dominant that
          IPX/SPX is now only rarely used.
        ✦ AppleTalk: Apple computers have their own suite of network protocols
          known as AppleTalk. The AppleTalk suite includes a Physical and Data
          Link layer protocol called LocalTalk, but can also work with standard
          lower-level protocols, including Ethernet and Token Ring.
        ✦ SNA: Systems Network Architecture is an IBM networking architecture
          that dates back to the 1970s, when mainframe computers roamed the
          earth and PCs had barely emerged from the primordial computer soup.
          SNA was designed primarily to support huge terminals such as airline
          reservation and banking systems, with tens of thousands of terminals
          attached to central host computers. Now that IBM mainframes support
          TCP/IP and terminal systems have all but vanished, SNA is beginning to
          fade away. Still, many networks that incorporate mainframe computers
          have to contend with SNA.
42   Book I: Networking Basics
          Chapter 3: Understanding
          Network Hardware
          In This Chapter
          ✓ Introducing servers
          ✓ Working with network interface cards
          ✓ Becoming familiar with network cable, network hubs, and switches
          ✓ Exploring repeaters, bridges, and routers
          ✓ Figuring out network storage




          T  he building blocks of networks are network hardware devices such as
             servers, adapter cards, cables, hubs, switches, routers, and so on. This
          chapter provides an overview of these building blocks.



Servers
          Server computers are the lifeblood of any network. Servers provide the
          shared resources that network users crave, such as file storage, databases,
          e-mail, Web services, and so on. Choosing the equipment you use for your
          network’s servers is one of the key decisions you’ll make when you set up a
          network. In the following sections, I describe some of the various ways you
          can equip your network’s servers.

          Right off the bat, I want to make one thing clear: Only the smallest networks
          can do without at least one dedicated server computer. For a home network
          or a small office network with only a few computers, you can get away with
          true peer-to-peer networking. That’s where each client computer shares its
          resources such as file storage or printers, and a dedicated server computer
          isn’t needed. For a more-detailed explanation of why this isn’t a good idea
          for larger networks, see Book II, Chapter 1.


          What’s important in a server
          Here are some general things to keep in mind when picking a server com-
          puter for your network:
44   Servers


         ✦ Scalability: Scalability refers to the ability to increase the size and
           capacity of the server computer without unreasonable hassle. It’s a
           major mistake to purchase a server computer that just meets your cur-
           rent needs because, you can rest assured, your needs will double within
           a year. If at all possible, equip your servers with far more disk space,
           RAM, and processor power than you currently need.
         ✦ Reliability: The old adage “you get what you pay for” applies especially
           well to server computers. Why spend $10,000 on a server computer
           when you can buy one with seemingly similar specifications at a dis-
           count electronics store for $2,000?
               One reason is reliability. When a client computer fails, only the person
               who uses that computer is affected. When a server fails, however, every-
               one on the network is affected. The less-expensive computer is probably
               made of inferior components that are more likely to fail.
         ✦ Availability: This concept of availability is closely related to reliabil-
           ity. When a server computer fails, how long does it take to correct the
           problem and get the server up and running again? Server computers are
           designed so their components can be easily diagnosed and replaced,
           which minimizes the downtime that results when a component fails. In
           some servers, components are hot swappable, which means that certain
           components can be replaced without shutting down the server. Some
           servers are designed to be fault-tolerant so that they can continue to
           operate even if a major component fails.
         ✦ Service and support: Service and support are factors often overlooked
           when picking computers. If a component in a server computer fails, do
           you have someone on site qualified to repair the broken computer? If
           not, you should get an on-site maintenance contract for the computer.
           Don’t settle for a maintenance contract that requires you to take the
           computer in to a repair shop or, worse, mail it to a repair facility. You
           can’t afford to be without your server that long.


        Components of a server computer
        The hardware components that comprise a typical server computer are simi-
        lar to the components used in less expensive client computers. However,
        server computers are usually built from higher-grade components than
        client computers for the reasons given in the preceding section. The follow-
        ing paragraphs describe the typical components of a server computer:

         ✦ Motherboard: The motherboard is the computer’s main electronic
           circuit board to which all the other components of your computer are
           connected. More than any other component, the motherboard is the
           computer. All other components attach to the motherboard.
                                                            Servers       45

   The major components on the motherboard include the processor (or               Book I
   CPU), supporting circuitry called the chipset, memory, expansion slots,        Chapter 3
   a standard IDE hard drive controller, and I/O ports for devices such as




                                                                                     Network Hardware
   keyboards, mice, and printers. Some motherboards also include addi-




                                                                                       Understanding
   tional built-in features such as a graphic adapter, SCSI disk controller, or
   network interface.
✦ Processor: The processor, or CPU, is the brain of the computer.
  Although the processor isn’t the only component that affects overall
  system performance, it’s the one that most people think of first when
  deciding what type of server to purchase. At the time of this writing,
  Intel had two processor models specifically designed for use in server
  computers, as summarized in Table 3-1.
   Each motherboard is designed to support a particular type of processor.
   CPUs come in two basic mounting styles: slot or socket. However, you
   can choose from several types of slots and sockets, so you have to make
   sure that the motherboard supports the specific slot or socket style
   used by the CPU. Some server motherboards have two or more slots or
   sockets to hold two or more CPUs.
   The term clock speed refers to how fast the basic clock that drives the pro-
   cessor’s operation ticks. In theory, the faster the clock speed, the faster
   the processor. However, clock speed alone is reliable only for comparing
   processors within the same family. In fact, the Itanium processors are
   faster than Xeon processors at the same clock speed. That’s because the
   Itanium processor models contain more advanced circuitry than the older
   model, so they can accomplish more work with each tick of the clock.
   The number of processor cores also has a dramatic effect on perfor-
   mance. Each processor core acts as if it’s a separate processor. Most
   server computers use dual-core (two processor cores) or quad-core
   (four cores) chips.



 Table 3-1                        Intel Processors
 Processor                 Clock Speed                Processor Cores
 Itanium 9300              1.60–1.73GHz               4
 Xeon                      1.83–3.4GHz                2–6


✦ Memory: Don’t scrimp on memory. People rarely complain about serv-
  ers having too much memory. Many different types of memory are avail-
  able, so you have to pick the right type of memory to match the memory
  supported by your motherboard. The total memory capacity of the
  server depends on the motherboard. Most new servers can support at
  least 16GB of memory, and some can handle up to 256GB.
46   Servers


         ✦ Hard drives: Most desktop computers use inexpensive hard drives
           called SATA drives. These drives are adequate for individual users, but
           because performance is more important for servers, another type of
           drive known as SCSI is usually used instead. For the best performance,
           use the SCSI drives along with a high-performance SCSI controller card.
           (However, because of its low cost, SATA drives are often used in inex-
           pensive servers.)
         ✦ Network connection: The network connection is one of the most impor-
           tant parts of any server. Many servers have network adapters built into
           the motherboard. If your server isn’t equipped as such, you’ll need
           to add a separate network adapter card. See the section, “Network
           Interface Cards,” later in this chapter, for more information.
         ✦ Video: Fancy graphics aren’t that important for a server computer.
           You can equip your servers with inexpensive generic video cards and
           monitors without affecting network performance. (This is one of the few
           areas where it’s acceptable to cut costs on a server.)
         ✦ Power supply: Because a server usually has more devices than a typi-
           cal desktop computer, it requires a larger power supply (typically 300
           watts). If the server houses a large number of hard drives, it may require
           an even larger power supply.


        Server form factors
        The term form factor refers to the size, shape, and packaging of a hardware
        device. Server computers typically come in one of three form factors:

         ✦ Tower case: Most servers are housed in a traditional tower case, similar
           to the tower cases used for desktop computers. A typical server tower
           case is 18-inches high, 20-inches deep, and 9-inches wide and has room
           inside for a motherboard, five or more hard drives, and other compo-
           nents. Tower cases also come with built-in power supplies.
               Some server cases include advanced features specially designed for
               servers, such as redundant power supplies (so both servers can con-
               tinue operating if one of the power supplies fails), hot-swappable fans,
               and hot-swappable disk drive bays. (Hot-swappable components can be
               replaced without powering down the server.)
         ✦ Rack mount: If you need only a few servers, tower cases are fine. You
           can just place the servers next to each other on a table or in a cabinet
           that’s specially designed to hold servers. If you need more than a few
           servers, though, space can quickly become an issue. For example, what
           if your departmental network requires a bank of ten file servers? You’d
           need a pretty long table.
                                                                              Servers        47

               Rack-mount servers are designed to save space when you need more                    Book I
               than a few servers in a confined area. A rack-mount server is housed in            Chapter 3
               a small chassis that’s designed to fit into a standard 19-inch equipment




                                                                                                     Network Hardware
               rack. The rack allows you to vertically stack servers in order to save




                                                                                                       Understanding
               space.
            ✦ Blade servers: Blade servers are designed to save even more space than
              rack-mount servers. A blade server is a server on a single card that can
              be mounted alongside other blade servers in a blade chassis, which
              itself fits into a standard 19-inch equipment rack. A typical blade chassis
              holds six or more servers, depending on the manufacturer.
               One of the key benefits of blade servers is that you don’t need a sepa-
               rate power supply for each server. Instead, the blade enclosure provides
               power for all its blade servers. Some blade server systems provide
               rack-mounted power supplies that can serve several blade enclosures
               mounted in a single rack.
               In addition, the blade enclosure provides KVM switching so that you
               don’t have to use a separate KVM switch. You can control any of the
               servers in a blade server network from a single keyboard, monitor, and
               mouse. (For more information, see the sidebar, “Saving space with a
               KVM switch.”)
               One of the biggest benefits of blade servers is that they drastically cut
               down the amount of cable clutter. With rack-mount servers, each server
               requires its own power cable, keyboard cable, video cable, mouse cable,
               and network cables. With blade servers, a single set of cables can ser-
               vice all the servers in a blade enclosure.




                 Saving space with a KVM switch
If you have more than two or three servers in      computers. More elaborate KVM switches can
one location, you should consider getting a        control more computers, using a pop-up menu
device called a KVM switch to save space. A        or a special keyboard combination to switch
KVM switch lets you connect several server         among computers. Some advanced KVMs can
computers to a single keyboard, monitor, and       even control a mix of PCs and Macintosh com-
mouse. (KVM stands for keyboard, video, and        puters from a single keyboard, monitor, and
mouse.) Then, you can control any of the serv-     mouse.
ers from a single keyboard, monitor, and mouse
                                                   To find more information about KVM switches,
by turning a dial or by pressing a button on the
                                                   go to a Web search engine such as Google and
KVM switch.
                                                   search for “KVM.”
Simple KVM switches are mechanical affairs
that let you choose from among 2 to 16 or more
48   Network Interface Cards


Network Interface Cards
        Every computer on a network, both clients and servers, requires a network
        interface card (or NIC) in order to access the network. A NIC is usually a
        separate adapter card that slides into one of the server’s motherboard
        expansion slots. However, most newer computers have the NIC built into the
        motherboard, so a separate card isn’t needed.

        For client computers, you can usually get away with using the inexpensive
        built-in NIC because client computers are used to connect only one user to
        the network. However, the NIC in a server computer connects many net-
        work users to the server. As a result, it makes sense to spend more money
        on a higher-quality NIC for a heavily used server. Most network adminis-
        trators prefer to use name-brand cards from manufacturers such as Intel,
        SMC, or 3Com.

        Most NICs made today support 1 Gbps networking and will also support
        slower 100 Mbps and even ancient 10 Mbps networks. These cards automati-
        cally adjust their speed to match the speed of the network. So you can use
        a gigabit card on a network that has older 100 Mbps cards without trouble.
        You can find inexpensive gigabit cards for as little as $5 each, but a typical
        name-brand card (such as Linksys or Intel) will cost around $25 or $30.

        Here are a few other points to ponder concerning network interface cards:

         ✦ A NIC is a Physical layer and Data Link layer device. Because a NIC
           establishes a network node, it must have a physical network address,
           also known as a MAC address. The MAC address is burned into the NIC
           at the factory, so you can’t change it. Every NIC ever manufactured has a
           unique MAC address.
         ✦ For server computers, it makes sense to use more than one NIC. That
           way, the server can handle more network traffic. Some server NICs have
           two or more network interfaces built into a single card.
         ✦ Fiber-optic networks also require NICs. Fiber-optic NICs are still too
           expensive for desktop use in most networks. Instead, they’re used for
           high-speed backbones. If a server connects to a high-speed fiber back-
           bone, it will need a fiber-optic NIC that matches the fiber-optic cable
           being used.



Network Cable
        Nearly all modern networks are constructed using a type of cable called
        twisted-pair cable, which looks a little like phone cable but is subtly different.
                                                                  Network Cable         49

              You may encounter other types of cable in an existing network: coax cable         Book I
              that resembles TV cable, thick yellow cable that used to be the only type of     Chapter 3
              cable used for Ethernet, fiber-optic cables that span long distances at high




                                                                                                  Network Hardware
              speeds, or thick twisted-pair bundles that carry multiple sets of twisted-pair




                                                                                                    Understanding
              cable between wiring closets in a large building. But as I mentioned, it’s
              twisted-pair cable for nearly all new networks.

              A choice that’s becoming more popular every day is to forego network
              cable and instead build your network using wireless network components.
              Because Book V is devoted exclusively to wireless networking, I don’t
              describe wireless network components in this chapter.


              Coaxial cable
              A type of cable that was once popular for Ethernet networks is coaxial cable,
              sometimes called thinnet or BNC cable because of the type of connectors
              used on each end of the cable. Thinnet cable operates only at 10 Mbps and is
              rarely used for new networks. However, you’ll find plenty of existing thinnet
              networks still being used. Figure 3-1 shows a typical coaxial cable.




Figure 3-1:
Coax cable.



              Here are some salient points about coaxial cable:

               ✦ You attach thinnet to the network interface card by using a goofy twist-
                 on connector called a BNC connector. You can purchase preassembled
                 cables with BNC connectors already attached in lengths of 25 or 50 feet,
                 or you can buy bulk cable on a big spool and attach the connectors
                 yourself by using a special tool. (I suggest buying preassembled cables.
                 Attaching connectors to bulk cable can be tricky.)
               ✦ With coaxial cables, you connect your computers point-to-point in a
                 bus topology. At each computer, a T connector is used to connect two
                 cables to the network interface card.
               ✦ A special plug called a terminator is required at each end of a series of
                 thinnet cables. The terminator prevents data from spilling out the end of
                 the cable and staining the carpet.
50      Network Cable


                ✦ The cables strung end-to-end from one terminator to the other are col-
                  lectively called a segment. The maximum length of a thinnet segment is
                  about 200 meters (actually, 185 meters). You can connect as many as 30
                  computers on one segment. To span a distance greater than 185 meters
                  or to connect more than 30 computers, you must use two or more seg-
                  ments with a device called a repeater to connect each segment.
                ✦ Although Ethernet coaxial cable resembles TV coaxial cable, the two
                  types of cable aren’t interchangeable. Don’t try to cut costs by wiring
                  your network with cheap TV cable.


               Twisted-pair cable
               The most popular type of cable today is twisted-pair cable, or UTP. (The U
               stands for unshielded, but no one says unshielded twisted pair. Just twisted
               pair will do.) UTP cable is even cheaper than thin coaxial cable, and best
               of all, many modern buildings are already wired with twisted-pair cable
               because this type of wiring is often used with modern phone systems.
               Figure 3-2 shows a twisted-pair cable.




Figure 3-2:
Twisted-pair
cable.



               When you use UTP cable to construct an Ethernet network, you connect the
               computers in a star arrangement. In the center of the star is a device called a
               hub. Depending on the model, Ethernet hubs enable you to connect from 4 to
               24 computers using twisted-pair cable.

               An advantage of UTP’s star arrangement is that if one cable goes bad, only
               the computer attached to that cable is affected; the rest of the network con-
               tinues to chug along. With coaxial cable, a bad cable affects the entire net-
               work, and not just the computer to which the bad cable is connected.

               Here are a few other details that you should know about twisted-pair cabling:

                ✦ UTP cable consists of pairs of thin wire twisted around each other;
                  several such pairs are gathered up inside an outer insulating jacket.
                  Ethernet uses two pairs of wires, or four wires altogether. The number
                  of pairs in a UTP cable varies, but it’s often more than two.
                ✦ UTP cable comes in various grades called Categories. Don’t use anything
                  less than Category 5e cable for your network. Although cheaper, it may
                  not be able to support faster networks.
                                                                   Switches        51

           Although higher-Category cables are more expensive than lower-Category           Book I
           cables, the real cost of installing Ethernet cabling is the labor required to   Chapter 3
           actually pull the cables through the walls. As a result, I recommend that




                                                                                              Network Hardware
           you always spend the extra money to buy Category 5e cable.




                                                                                                Understanding
       ✦ If you want to sound like you know what you’re talking about, say “Cat
         5e” instead of “Category 5e.”
       ✦ Many existing networks are cabled with Category 5 cable, which is fine
         for 100Mbps networks but isn’t rated for Gigabit networks. Category
         5e cable (the e stands for enhanced) and Category 6 cable will support
         1,000 Mbps networks.
       ✦ UTP cable connectors look like modular phone connectors but are a bit
         larger. UTP connectors are officially called RJ-45 connectors.
       ✦ Like thinnet cable, UTP cable is also sold in prefabricated lengths.
         However, RJ-45 connectors are much easier to attach to bulk UTP cable
         than BNC cables are to attach to bulk coaxial cable. As a result, I suggest
         that you buy bulk cable and connectors unless your network consists of
         just two or three computers. A basic crimp tool to attach the RJ-45 con-
         nectors costs about $50.
       ✦ The maximum allowable cable length between the hub and the com-
         puter is 100 meters (about 328 feet).



Switches
      The biggest difference between using coaxial cable and twisted-pair cable is
      that when you use twisted-pair cable, you also must use a separate device
      called a switch. Years ago, switches were expensive devices — expensive
      enough that most do-it-yourself networkers who were building small net-
      works opted for thinnet cable in order to avoid the expense and hassle of
      using hubs.

      Nowadays, the cost of switches has dropped so much that the advantages
      of twisted-pair cabling outweigh the hassle and cost of using switches. With
      twisted-pair cabling, you can more easily add new computers to the net-
      work, move computers, find and correct cable problems, and service the
      computers that you need to remove from the network temporarily.

      Note that in some older networks, you may see a device known as a hub used
      instead of a switch. Hubs used to be used because they were less expen-
      sive than switches. However, the cost of switches came down dramatically,
      pushing hubs into relic status. If you have an older network that uses hubs
      and seems to run slowly, you can probably improve the network’s speed by
      replacing the older hubs with newer switches. For more information, see the
      sidebar, “Hubs and switches demystified,” later in this chapter.
52        Switches




                        Hubs and switches demystified
     Both hubs and switches let you connect mul-            connected to the hub get to see the packet
     tiple computers to a twisted-pair network.             so that they can determine whether the
     Switches are more efficient than hubs, but not         packet was intended for them.
     just because they’re faster. If you really want
                                                         ✓ A switch is a Data Link layer device, which
     to know, here’s the actual difference between
                                                            means it’s able to look into the packets
     a hub and a switch:
                                                            that pass through it to examine a critical
     ✓ In a hub, every packet that arrives at the           piece of Data Link layer information: the
         hub on any of its ports is automatically sent      MAC address. With this information in
         out on every other port. The hub has to do         hand, a switch can keep track of which
         this because it’s a Physical layer device,         computer is connected to each of its ports.
         so it has no way to keep track of which            So if John’s computer on port 1 sends a
         computer is connected to each port. For            packet to Andrea’s computer on port 5,
         example, suppose that John’s computer              the switch receives the packet on port 1
         is connected to port 1 on an 8-port hub,           and then sends the packet out on port 5
         and Andrea’s computer is connected to              only. This process is not only faster, but
         port 5. If John’s computer sends a packet          also improves the security of the system
         of information to Andrea’s computer, the           because other computers don’t see pack-
         hub receives the packet on port 1 and then         ets that aren’t meant for them.
         sends it out on ports 2–8. All the computers



               If you use twisted-pair cabling, you need to know some of the ins and outs of
               using hubs:

                 ✦ Because you must run a cable from each computer to the switch, find a
                   central location for the switch to which you can easily route the cables.
                 ✦ The switch requires electrical power, so make sure that an electrical
                   outlet is handy.
                 ✦ When you purchase a switch, purchase one with at least twice as many
                   connections as you need. Don’t buy a four-port switch if you want to net-
                   work four computers because when (not if) you add the fifth computer,
                   you have to buy another switch.
                 ✦ You can connect switches to one another, as shown in Figure 3-3; this is
                   called daisy chaining. When you daisy chain switches, you connect one
                   end of a cable to a port on one switch and the other end to a port on the
                   other switch. Note that on some switches, you must use a special des-
                   ignated port for daisy chaining. So be sure to read the instructions that
                   come with the switch to make sure that you daisy chain it properly.
                                                                   Switches       53

                                                                                         Book I
                                                                                        Chapter 3




                                                                                           Network Hardware
                                                                                             Understanding
                                   Switch



                                      Switch




Figure 3-3:
Daisy
chaining
switches
together.



              ✦ You can daisy chain no more than three switches together. If you have
                more computers than three hubs can accommodate, don’t panic. For a
                small additional cost, you can purchase hubs that have a BNC connec-
                tion on the back. Then you can string the hubs together using thinnet
                cable. The three-hub limit doesn’t apply when you use thinnet cable
                to connect the hubs. You can also get stackable switches that have
                high-speed direct connections that enable two or more switches to be
                counted as a single switch.
              ✦ When you shop for network hubs, you may notice that the expensive
                ones have network-management features that support something called
                SNMP. These hubs are called managed hubs. Unless your network is very
                large and you know what SNMP is, don’t bother with the more expensive
                managed hubs. You’d be paying for a feature that you may never use.
54   Repeaters


         ✦ For large networks, you may want to consider using a managed switch.
           A managed switch allows you to monitor and control various aspects
           of the switch’s operation from a remote computer. The switch can alert
           you when something goes wrong with the network, and it can keep
           performance statistics so that you can determine which parts of the net-
           work are heavily used and which aren’t. A managed switch costs two or
           three times as much as an unmanaged switch, but for larger networks,
           the benefits of managed switches are well worth the additional cost.



Repeaters
        A repeater (sometimes called an extender) is a gizmo that gives your net-
        work signals a boost so that the signals can travel farther. It’s kind of like a
        Gatorade station in a marathon. As the signals travel past the repeater, they
        pick up a cup of Gatorade, take a sip, splash the rest of it on their heads,
        toss the cup, and hop in a cab when they’re sure that no one is looking.

        You need a repeater when the total length of a single span of network cable
        exceeds 100 meters (328 feet). The 100-meter length limit applies to the
        cable that connects a computer to the switch or the cable that connects
        switches to each other when switches are daisy chained together. In other
        words, you can connect each computer to the switch with no more than 100
        meters of cable, and you can connect switches to each other with no more
        than 100 meters of cable.

        Figure 3-4 shows how you can use a repeater to connect two groups of com-
        puters that are too far apart to be strung on a single segment. When you use
        a repeater like this, the repeater divides the cable into two segments. The
        cable length limit still applies to the cable on each side of the repeater.

        Here are some points to ponder when you lie awake tonight wondering
        about repeaters:

         ✦ Repeaters are not typically used with twisted-pair networks.
            Well, technically, that’s not true because the switches themselves func-
            tion as repeaters. So what I really meant is that you typically see repeat-
            ers as stand-alone devices only when a single cable segment would be
            more than 100 meters.
         ✦ A basic rule of Ethernet life is that a signal can’t pass through more than
           three repeaters on its way from one node to another. That doesn’t mean
           you can’t have more than three repeaters or switches, but if you do, you
           have to carefully plan the network cabling so that the three-repeater
           rule isn’t violated.
                                                                         Bridges        55

               ✦ Repeaters are legitimate components of a by-the-book Ethernet network.         Book I
                 They don’t extend the maximum length of a single segment; they just           Chapter 3
                 enable you to tie two segments together. Beware of the little black boxes




                                                                                                  Network Hardware
                 that claim to extend the segment limit beyond the standard 100-meter




                                                                                                    Understanding
                 limit for 10/100BaseT cable. These products usually work, but playing by
                 the rules is better.




                                   Switch



                                    Repeater                          Switch




Figure 3-4:
Using a
repeater.




Bridges
              A bridge is a device that connects two networks so that they act as if they’re
              one network. Bridges are used to partition one large network into two
              smaller networks for performance reasons. You can think of a bridge as a
              kind of smart repeater.
56   Bridges


        Repeaters listen to signals coming down one network cable, amplify them,
        and send them down the other cable. They do this blindly, paying no atten-
        tion to the content of the messages that they repeat.

        In contrast, a bridge is a little smarter about the messages that come down
        the pike. For starters, most bridges have the capability to listen to the
        network and automatically figure out the address of each computer on
        both sides of the bridge. Then the bridge can inspect each message that
        comes from one side of the bridge and broadcast it on the other side of
        the bridge, but only if the message is intended for a computer that’s on the
        other side.

        This key feature enables bridges to partition a large network into two
        smaller, more efficient networks. Bridges work best in networks that are
        highly segregated. For example (humor me here — I’m a Dr. Seuss fan), sup-
        pose that the Sneetches networked all their computers and discovered that,
        although the Star-Bellied Sneetches’ computers talked to each other fre-
        quently and the Plain-Bellied Sneetches’ computers also talked to each other
        frequently, rarely did a Star-Bellied Sneetch’s computer talk to a Plain-Bellied
        Sneetch’s computer.

        A bridge can partition the Sneetchnet into two networks: the Star-Bellied net-
        work and the Plain-Bellied network. The bridge automatically learns which
        computers are on the Star-Bellied network and which are on the Plain-Bellied
        network. The bridge forwards messages from the Star-Bellied side to the
        Plain-Bellied side (and vice versa) only when necessary. The overall perfor-
        mance of both networks improves, although the performance of any network
        operation that has to travel over the bridge slows down a bit.

        Here are a few additional things to consider about bridges:

         ✦ Some bridges also have the capability to translate the messages from
           one format to another. For example, if the Star-Bellied Sneetches build
           their network with Ethernet and the Plain-Bellied Sneetches use Token
           Ring, a bridge can tie the two together.
         ✦ You can get a basic bridge to partition two Ethernet networks for about
           $500 from mail order suppliers. More sophisticated bridges can cost as
           much as $5,000 or more.
         ✦ For simple bridge applications, you don’t need an expensive special-
           ized bridge device; instead, you can just use a switch. That’s because a
           switch is effectively a multi-port bridge.
         ✦ If you’ve never read Dr. Seuss’s classic story of the Sneetches, you
           should.
                                                                       Routers        57

Routers                                                                                        Book I
                                                                                              Chapter 3
          A router is like a bridge, but with a key difference. Bridges are Data Link layer




                                                                                                 Network Hardware
          devices, so they can tell the MAC address of the network node to which each




                                                                                                   Understanding
          message is sent, and can forward the message to the appropriate segment.
          However, they can’t peek into the message itself to see what type of informa-
          tion is being sent. In contrast, a router is a Network layer device, so it can
          work with the network packets at a higher level. In particular, a router can
          examine the IP address of the packets that pass through it. And because IP
          addresses have both a network and a host address, a router can determine
          what network a message is coming from and going to. Bridges are ignorant of
          this information.

          One key difference between a bridge and a router is that a bridge is essen-
          tially transparent to the network. In contrast, a router is itself a node on the
          network, with its own MAC and IP addresses. This means that messages can
          be directed to a router, which can then examine the contents of the message
          to determine how it should handle the message.

          You can configure a network with several routers that can work coopera-
          tively together. For example, some routers are able to monitor the network
          to determine the most efficient path for sending a message to its ultimate
          destination. If a part of the network is extremely busy, a router can automati-
          cally route messages along a less-busy route. In this respect, the router is
          kind of like a traffic reporter up in a helicopter. The router knows that the
          101 is bumper-to-bumper all the way through Sunnyvale, so it sends the mes-
          sage on 280 instead.

          Here’s some additional information about routers:

           ✦ The functional distinctions between bridges and routers — and switches
             and hubs, for that matter — get blurrier all the time. As bridges, hubs,
             and switches become more sophisticated, they’re able to take on some
             of the chores that used to require a router, thus putting many routers
             out of work.
           ✦ Some routers are nothing more than computers with several network
             interface cards and special software to perform the router functions.
           ✦ Routers can also connect networks that are geographically distant from
             each other via a phone line (using modems) or ISDN.
           ✦ You can also use a router to join your LAN to the Internet. Figure 3-5
             shows a router used for this purpose.
58       Network Attached Storage




                                     Switch
Figure 3-5:
Connecting
to the
Internet                                                           The
                                      Router                     Internet
with a
router.




Network Attached Storage
              Many network servers exist solely for the purpose of making disk space
              available to network users. As networks grow to support more users, and
              users require more disk space, network administrators are constantly find-
              ing ways to add more storage to their networks. One way to do that is to add
              more file servers. However, a simpler and less expensive way is to use net-
              work attached storage, also known as NAS.

              A NAS device is a self-contained file server that’s preconfigured and ready
              to run. All you have to do to set it up is take it out of the box, plug it in, and
              turn it on. NAS devices are easy to set up and configure, easy to maintain,
              and less expensive than traditional file servers.

              NAS should not be confused with a related technology called storage area
              networks, or SAN. SAN is a much more complicated and expensive technol-
              ogy that provides huge quantities of data storage for large networks. For
              more information on SAN, see the sidebar, “SAN is NAS spelled backwards.”

              A typical entry-level NAS device is the Dell PowerVault NX300. This device is
              a self-contained file server built into a small rack-mount chassis. It supports
              up to four hard drives with a total capacity up to four terabyte (or 4,000GB).
              The NX300 uses a Xeon processor and two built-in gigabit network ports.
                                                                    Network Printers             59

                                                                                                        Book I
                                                                                                       Chapter 3
                   SAN is NAS spelled backwards




                                                                                                          Network Hardware
 It’s easy to confuse the terms storage area       consists of three components: storage devices




                                                                                                            Understanding
 network (SAN) and network attached storage        (perhaps hundreds of them), a separate high-
 (NAS). Both refer to relatively new network       speed network (usually fiber-optic) that directly
 technologies that let you manage the disk stor-   connects the storage devices to each other,
 age on your network. However, NAS is a much       and one or more SAN servers that connect the
 simpler and less expensive technology. A NAS      SAN to the local area network. The SAN server
 device is nothing more than an inexpensive        manages the storage devices attached to the
 self-contained file server. Using NAS devices     SAN and allows users of the LAN to access the
 actually simplifies the task of adding storage    storage.
 to a network because the NAS eliminates
                                                   Setting up and managing a storage area net-
 the chore of configuring a network operating
                                                   work is a job for a SAN expert. For more infor-
 system for routine file-sharing tasks.
                                                   mation about storage area networks, see the
 A storage area network is designed for manag-     home page of the Storage Networking Industry
 ing very large amounts of network storage —       Association at www.snia.org.
 sometimes downright huge amounts. A SAN



           The Dell NX300 runs a special version of Windows Server 2008 called the
           Windows Storage Server 2008. This version of Windows is designed specifi-
           cally for NAS devices. It allows you to configure the network storage from
           any computer on the network by using a Web browser.

           Note that some NAS devices use customized versions of Linux rather than
           Windows Storage Server. Also, in some systems, the operating system
           resides on a separate hard drive that’s isolated from the shared disks. This
           prevents the user from inadvertently damaging the operating system.



Network Printers
           Although you can share a printer on a network by attaching the printer to a
           server computer, many printers have network interfaces built in. This lets
           you connect the printer directly to the network. Then network users can
           connect to the printer and use it without going through a server.

           Even if you connect a printer directly to the network, it’s still a good idea to
           have the printer managed by a server computer running a network operat-
           ing system such as Windows Server 2003 or 2007. That way, the server can
           store print jobs sent to the printer by multiple users and print the jobs in the
           order in which they were received.
60   Book I: Networking Basics
      Chapter 4: Understanding Network
      Operating Systems
      In This Chapter
      ✓ Understanding what network operating systems do
      ✓ Figuring out the advantages of Windows Server 2003
      ✓ Analyzing Windows 2000 Server
      ✓ Taking a look at Windows NT Server
      ✓ Navigating NetWare
      ✓ Delving into peer-to-peer networking
      ✓ Exploring other network operating systems




      O     ne of the basic choices that you must make before you proceed any
            further is to decide which network operating system (NOS) to use as
      the foundation for your network. This chapter begins with a description of
      several important features found in all network operating systems. Next,
      it provides an overview of the advantages and disadvantages of the most
      popular network operating systems.



Network Operating System Features
      All network operating systems, from the simplest to the most complex, must
      provide certain core functions. These include the ability to connect to other
      computers on the network, share files and other resources, provide for
      security, and so on. In the following sections, I describe some of these core
      NOS features in general terms.


      Network support
      It goes without saying that a network operating system should support net-
      works. (I can picture Mike Myers in his classic Saturday Night Live role as
      Linda Richman, host of Coffee Talk, saying “I’m getting a little verklempt. . . .
      Talk amongst yourselves. . . . I’ll give you a topic — network operating sys-
      tems do not network, nor do they operate. Discuss.”)
62   Network Operating System Features


        A network operating system must support a wide variety of networking pro-
        tocols in order to meet the needs of its users. That’s because a large network
        typically consists of a mixture of various versions of Windows, as well as a
        few scattered Macintosh (mostly in the art department) and possibly some
        Linux computers. The computers often have distinct protocols.

        Many servers have more than one network interface card installed. In
        that case, the NOS must be able to support multiple network connections.
        Ideally, the NOS should have the ability to balance the network load among
        its network interfaces. In addition, in the event that one of the connections
        fails, the NOS should be able to seamlessly switch to another connection.

        Finally, most network operating systems include a built-in ability to function
        as a router that connects two networks. The NOS router functions should
        also include firewall features in order to keep unauthorized packets from
        entering the local network.


        File-sharing services
        One of the most important functions of a network operating system is its
        ability to share resources with other network users. The most common
        resource that’s shared is the server’s file system. A network server must
        be able to share some or all of its disk space with other users so that those
        users can treat the server’s disk space as an extension of their own comput-
        ers’ disk spaces.

        The NOS allows the system administrator to determine which portions of the
        server’s file system to share. Although an entire hard drive can be shared, it
        isn’t commonly done. Instead, individual directories or folders are shared.
        The administrator can control which users are allowed to access each
        shared folder.

        Because file sharing is the reason many network servers exist, network oper-
        ating systems have more sophisticated disk management features than are
        found in desktop operating systems. For example, most network operating
        systems have the ability to manage two or more hard drives as if they were
        a single drive. In addition, most can create mirrors, which automatically keep
        backup copies of drives on a second drive.


        Multitasking
        Only one user at a time uses a desktop computer; however, multiple users
        simultaneously use server computers. As a result, a network operating
        system must provide support for multiple users who access the server
        remotely via the network.
                            Network Operating System Features              63

At the heart of multiuser support is multitasking, which is the ability of an       Book I
operating system to execute more than one program — called a task or a             Chapter 4
process — at a time. Multitasking operating systems are like the guy who




                                                                                   Network Operating
used to spin plates balanced on sticks on the old Ed Sullivan Show. He’d




                                                                                    Understanding
run from plate to plate, trying to keep them all spinning so they wouldn’t




                                                                                       Systems
fall off the sticks. To make it challenging, he’d do it blindfolded or riding on
a unicycle.

Although multitasking creates the appearance that two or more programs
are executing on the computer at one time, in reality, a computer with a
single processor can execute only one program at a time. The operating
system switches the CPU from one program to another to create the appear-
ance that several programs are executing simultaneously, but at any given
moment, only one of the programs is actually executing. The others are
patiently waiting for their turns. (However, if the computer has more than
one CPU, the CPUs can execute programs simultaneously, which is called
multiprocessing.)

To see multitasking in operation on a Windows computer, press
Ctrl+Alt+Delete to bring up the Windows Task Manager and then click the
Processes tab. All the tasks currently active on the computer appear.

For multitasking to work reliably, the network operating system must com-
pletely isolate the executing programs from each other. Otherwise, one
program may perform an operation that adversely affects another program.
Multitasking operating systems do this by providing each task with its own
unique address space that makes it almost impossible for one task to affect
memory that belongs to another task.

In most cases, each program executes as a single task or process within the
memory address space allocated to the task. However, a single program can
also be split into several tasks. This technique is usually called multithread-
ing, and the program’s tasks are called threads.

The two approaches to multitasking are preemptive and non-preemptive. In
preemptive multitasking, the operating system decides how long each task
gets to execute before it should step aside so that another task can execute.
When a task’s time is up, the operating system’s task manager interrupts the
task and switches to the next task in line. All the network operating systems
in widespread use today use preemptive multitasking.

The alternative to preemptive multitasking is non-preemptive multitask-
ing. In non-preemptive multitasking, each task that gets control of the CPU is
allowed to run until it voluntarily gives up control so that another task can
run. Non-preemptive multitasking requires less operating system overhead
because the operating system doesn’t have to keep track of how long each
task has run. However, programs have to be carefully written so that they
don’t hog the computer all to themselves.
64   Network Operating System Features


        Directory services
        Directories are everywhere. When you need to make a phone call, you look
        up the number in a phone directory. When you need to find the address of a
        client, you look up his or her name in your Rolodex. And when you need to
        find the Sam Goody store at a shopping mall, you look for the mall directory.

        Networks have directories, too. Network directories provide information
        about the resources that are available on the network, such as users, com-
        puters, printers, shared folders, and files. Directories are an essential part of
        any network operating system.

        In early network operating systems, such as Windows NT 3.1 and NetWare
        3.x, each server computer maintained its own directory database of
        resources that were available on just that server. The problem with that
        approach was that network administrators had to maintain each directory
        database separately. That wasn’t too bad for networks with just a few serv-
        ers, but maintaining the directory on a network with dozens or even hun-
        dreds of servers was next to impossible.

        In addition, early directory services were application specific. For example,
        a server would have one directory database for user logins, another for file
        sharing, and yet another for e-mail addresses. Each directory had its own
        tools for adding, updating, and deleting directory entries.

        Most modern networks — particularly those based on Windows servers —
        use a directory service called Active Directory. Active Directory is essentially
        a database that organizes information about a network and allows users and
        computers to gain permission to access network resources. Active Directory
        is simple enough to use for small networks with just a few dozen computers
        and users, but powerful enough to work with large networks containing tens
        of thousands of computers.


        Security services
        All network operating systems must provide some measure of security to
        protect the network from unauthorized access. Hacking seems to be the
        national pastime these days. With most computer networks connected to
        the Internet, anyone anywhere in the world can and probably will try to
        break into your network.

        The most basic type of security is handled through user accounts, which
        grant individual users the right to access the network resources — and
        govern what resources each user can access. User accounts are secured
        by passwords; therefore, good password policy is a cornerstone of any secu-
        rity system. Most network operating systems let you establish password
                                           Microsoft’s Server Operating Systems                  65

            policies, such as requiring that passwords have a minimum length and                        Book I
            include a mix of letters and numerals. In addition, passwords can be set to                Chapter 4
            expire after a certain number of days, so users can be forced to frequently




                                                                                                       Network Operating
            change their passwords.




                                                                                                        Understanding
                                                                                                           Systems
            Most network operating systems also provide for data encryption, which
            scrambles data before it is sent over the network or saved on disk, and digi-
            tal certificates, which are used to ensure that users are who they say they are
            and files are what they claim to be.



Microsoft’s Server Operating Systems
            Over the years, Microsoft has released several versions of its Windows-
            based server operating system: Windows NT Server 4, Windows 2000 Server,
            Windows Server 2003, and Windows Server 2008. Windows Server 2008 is
            the newest version, but because it’s relatively new, many organizations are
            still using Windows Server 2003. In fact, some are still using Windows 2000
            Server, and there are probably a few (mostly on deserted islands cut off
            from civilization) running Windows NT Server 4.

            It’s useful to discuss these operating systems in the order they were
            released, because each new version builds on the previous version by intro-
            ducing new and improved features. However, keep in mind as you read the
            following sections that Windows NT Server 4 and Windows 2000 Server are
            considered obsolete, and Windows Server 2003 will be too in a few short
            years.




                                       NTFS drives
  All server versions of Windows use a spe-          ✓ NTFS drives provide better security fea-
  cial type of formatting for hard drives, differ-      tures than FAT drives. NTFS stores security
  ent from the standard FAT system used by              information on disk for each file and direc-
  MS-DOS since the early 1980s. (FAT stands             tory. In contrast, FAT has only rudimentary
  for File Allocation Table, in case you’re inter-      security features.
  ested.) The new system, called NTFS (for NT
                                                     ✓ NTFS drives are more reliable because
  File System), offers many advantages over FAT
                                                        NTFS keeps duplicate copies of important
  drives:
                                                        information, such as the location of each
  ✓ NTFS is much more efficient at using the            file on the hard drive. If a problem devel-
      space on your hard drive. As a result, NTFS       ops on an NTFS drive, Windows NT Server
      can cram more data onto a given hard              can probably correct the problem without
      drive than FAT.                                   losing any data. In contrast, FAT drives are
                                                        prone to losing information.
66   Microsoft’s Server Operating Systems


        Windows 2000 Server
        Windows 2000 Server built on the strengths of Windows NT Server 4 by
        adding new features that made Windows 2000 Server faster, easier to
        manage, more reliable, and easier to use for large and small networks alike.

        The most significant new feature offered by Windows 2000 Server is called
        Active Directory, which provides a single directory of all network resources
        and enables program developers to incorporate the directory into their pro-
        grams. Active Directory drops the 15-character domain and computer names
        in favor of Internet-style DNS names, such as Marketing.MyCompany.com or
        Sales.YourCompany.com. (However, it still supports the old-style names for
        older clients that don’t deal well with DNS names.)

        Windows 2000 Server came in three versions:

         ✦ Windows 2000 Server was the basic server, designed for small- to
           medium-sized networks. It included all the basic server features, includ-
           ing file and printer sharing, and acted as a Web and e-mail server.
         ✦ Windows 2000 Advanced Server was the next step up, designed for
           larger networks. Advanced Server could support server computers that
           have up to 8GB of memory (not hard drive — RAM!) and four integrated
           processors instead of the single processor that desktop computers and
           most server computers had.
         ✦ Windows 2000 Datacenter Server supported servers that have as many
           as 32 processors with up to 64GB of RAM and was specially designed for
           large database applications.

        For small networks with 50 or fewer computers, Microsoft offered a special
        bundle called the Small Business Server, which included the following com-
        ponents for one low, low price:

         ✦ Windows Server 2003: The operating system for your network server.
         ✦ Exchange Server 2003: For e-mail and instant messaging.
         ✦ SQL Server 2000: A database server.
         ✦ FrontPage 2000: For building Web sites.
         ✦ Outlook 2000: For reading e-mail.


        Windows Server 2003
        The next server version of Windows was Windows Server 2003. Windows
        Server 2003 built on Windows 2000 Server, with the following added features:
                          Microsoft’s Server Operating Systems           67

 ✦ A new-and-improved version of Active Directory with tighter security, an     Book I
   easier-to-use interface, and better performance.                            Chapter 4
 ✦ A better and easier-to-use system management interface, called the




                                                                               Network Operating
   Manage My Server window. On the flip side, for those who prefer brute-




                                                                                Understanding
   force commands, Windows Server 2003 includes a more comprehensive




                                                                                   Systems
   set of command line management tools than is offered by Windows 2000
   Server. Of course, the familiar Microsoft Management Console tools
   from Windows 2000 Server are still there.
 ✦ A major change in the application-programming interface for Windows
   programs, known as the .NET Framework.
 ✦ Support for ever-larger clusters of computers. A cluster is a set of com-
   puters that work together as if they were a single server. Windows 2000
   Server Datacenter Edition and previous versions supported clusters of
   four servers; Windows Server 2003 Enterprise and Datacenter Editions
   support clusters of eight servers. (Obviously, this is a benefit only for
   very large networks. The rest of us should just grin and say, “Cool!”)
 ✦ An enhanced distributed file system that lets you combine drives on sev-
   eral servers to create one shared volume.
 ✦ Support for storage area networks.
 ✦ A built-in Internet firewall to secure your Internet connection.
 ✦ A new version of Microsoft’s Web server, Internet Information Services
   (IIS) 6.0.

Like its predecessor, Windows Server 2003 comes in several versions. Four,
to be specific:

 ✦ Windows Server 2003, Standard Edition: This is the basic version of
   Windows 2003. If you’re using Windows Server 2003 as a file server or
   to provide other basic network services, this is the version you’ll use.
   Standard Edition can support servers with up to four processors and
   4GB of RAM.
 ✦ Windows Server 2003, Web Edition: A version of Windows 2003 opti-
   mized for use as a Web server.
 ✦ Windows Server 2003, Enterprise Edition: Designed for larger net-
   works, this version can support servers with up to eight processors,
   32GB of RAM, server clusters, and advanced features designed for high
   performance and reliability.
 ✦ Windows Server 2003, Datacenter Edition: The most powerful version
   of Windows 2003, with support for servers with 64 processors, 64GB of
   RAM, and server clusters, as well as advanced fault-tolerance features
   designed to keep the server running for mission-critical applications.
68   Other Server Operating Systems


        Windows Server 2008
        In February of 2008, Microsoft finally released the successor to Windows
        Server 2003, not surprisingly known as Windows Server 2008. Windows
        Server 2008 adds many new features to Windows Server 2003, including the
        following:

         ✦ Even more enhancements to Active Directory, including the ability to
           manage digital certificates, a new type of domain controller called a
           read-only domain controller, and the ability to stop and restart Active
           Directory services without shutting down the entire server.
         ✦ A new graphical user interface based on Windows Vista, including a new
           all-in-one management tool called the Server Manager.
         ✦ A new version of the operating system called Server Core, which has no
           graphical user interface. Server Core is run entirely from the command
           line or by a remote computer that connects to the server via Microsoft
           Management Console. Server Core is designed to provide efficient file
           servers, domain controllers, or DNS and DHCP servers.
         ✦ Remote connection enhancements that enable computers to establish
           Web-based connections to the server using the HTTPS protocol without
           having to establish a Virtual Private Network (VPN) connection.
         ✦ Yet another new version of the Internet Information Services (IIS) Web
           server (7.0).


        Windows Server 2008 R2
        In the fall of 2009, Microsoft issued an update to Windows Server 2008, offi-
        cially called Windows Server 2008 R2. Network administrators the world
        over rejoiced, in part because most of them are also Star Wars fans and they
        can now refer to their favorite operating system as “R2.”

        R2 builds on Windows Server 2008 with a variety of new features, including
        virtualization features that let you run more than one instance of the operat-
        ing system on a single server computer, a new version of IIS (7.5), and sup-
        port for up to 256 processors.

        Also, R2 officially drops support for 32-bit processors. In other words, R2
        only runs on server-class 64-bit processors such as Itanium and Xeon.



Other Server Operating Systems
        Although Windows Server is the most popular choice for network operat-
        ing systems, it isn’t the only game in town. The following sections briefly
        describe three other server choices: Linux, Macintosh OS/X Server, and
        Novell’s NetWare.
                                 Other Server Operating Systems             69

Linux                                                                               Book I
                                                                                   Chapter 4
Perhaps the most interesting operating system available today is Linux.
Linux is a free operating system that’s based on Unix, a powerful network




                                                                                   Network Operating
operating system often used on large networks. Linux was started by




                                                                                    Understanding
Linus Torvalds, who thought it would be fun to write a version of Unix in




                                                                                       Systems
his free time — as a hobby. He enlisted help from hundreds of program-
mers throughout the world, who volunteered their time and efforts via the
Internet. Today, Linux is a full-featured version of Unix; its users consider it
to be as good or better than Windows.

Linux offers the same networking benefits as Unix and can be an excellent
choice as a server operating system.


Apple Mac OS/X Server
All the other server operating systems I describe in this chapter run on
Intel-based PCs with Pentium or Pentium-compatible processors. But what
about Macintosh computers? After all, Macintosh users need networks, too.
For Macintosh networks, Apple offers a special network server operating
system known as Mac OS/X Server. Mac OS/X Server has all the features
you’d expect in a server operating system: file and printer sharing, Internet
features, e-mail, and so on.


Novell NetWare
NetWare was once the king of network operating systems. Today, NetWare
networks are rare, but you can still find them if you look hard enough.
NetWare has always had an excellent reputation for reliability. In fact, some
network administrators swear that they have NetWare servers on their net-
works that have been running continuously, without a single reboot, since
Ronald Reagan was president. (Unfortunately, there hasn’t been a major
upgrade to NetWare since George W. Bush’s first term.)

Novell released the first version of NetWare in 1983, two years before the
first version of Windows and four years before Microsoft’s first network
operating system, the now defunct LAN Manager. Over the years, NetWare
has gone through many versions. The most important versions were:

 ✦ NetWare version 3.x, the version that made NetWare famous. NetWare
   3.x used a now outdated directory scheme called the bindery. Each
   NetWare 3.x server has a bindery file that contains information about the
   resources on that particular server. With the bindery, you had to log on
   separately to each server that contained resources you wanted to use.
 ✦ NetWare 4.x, in which NetWare Directory Service, or NDS, replaced the
   bindery. NDS is similar to Active Directory. It provides a single directory
   for the entire network rather than separate directories for each server.
70   Peer-to-Peer Networking with Windows


         ✦ NetWare 5.x was the next step. It introduced a new user interface based
           on Java for easier administration, improved support for Internet proto-
           cols, multiprocessing with up to 32 processors, and many other features.
         ✦ NetWare 6.0 introduced a variety of new features, including a new disk
           management system called Novell Storage Services, Web-based access
           to network folders and printers, and built-in support for Windows, Linux,
           Unix, and Macintosh file systems.
         ✦ Novell released its last major version of NetWare (6.5) in summer 2003.
           It included improvements to its browser-based management tools and
           was bundled with open-source servers such as Apache and MySQL.

        Beginning in 2005, NetWare has transformed itself into a Linux-based system
        called Open Enterprise System (OES). In OES, the core of the operating
        system is actually Linux, with added applications that run the traditional
        NetWare services such as directory services. (For more information, see
        “Linux” earlier in this chapter.)



Peer-to-Peer Networking with Windows
        If you’re not up to the complexity of dedicated network operating systems,
        you may want to opt for a simple peer-to-peer network based on a desktop
        version of Windows.


        Advantages of peer-to-peer networks
        The main advantage of a peer-to-peer network is that it’s easier to set up
        and use than a network with a dedicated server. Peer-to-peer networks rely
        on the limited network server features that are built into Windows, such as
        the ability to share files and printers. Recent versions of Windows, including
        Windows 7, Vista, and Windows XP, include wizards that automatically con-
        figure a basic network for you so that you don’t have to manually configure
        any network settings.

        Another advantage of peer-to-peer networks is that they can be less expen-
        sive than server-based networks. Here are some of the reasons that peer-to-
        peer networks are inexpensive:

         ✦ Peer-to-peer networks don’t require you to use a dedicated server com-
           puter. Any computer on the network can function as both a network
           server and a user’s workstation. (However, you can configure a com-
           puter as a dedicated server if you want to. Doing so results in better per-
           formance but negates the cost benefit of not having a dedicated server
           computer.)
                        Peer-to-Peer Networking with Windows               71

 ✦ Peer-to-peer networks are easier to set up and use, which means that            Book I
   you can spend less time figuring out how to make the network work              Chapter 4
   and keep it working. And, as Einstein proved, time is money (hence his




                                                                                  Network Operating
   famous equation, E=M$2).




                                                                                   Understanding
 ✦ You must consider the cost of the server operating system itself.




                                                                                      Systems
   Windows Server can cost as much as $200 per user. And the total cost
   increases as your network grows, although the cost per user drops. For a
   peer-to-peer Windows server, you pay for Windows once. You don’t pay
   any additional charges based on the number of users on your network.


Drawbacks of peer-to-peer networks
Yes, peer-to-peer networks are easier to install and manage than domain-
based networks, but they do have their drawbacks:

 ✦ Because peer-to-peer networks are based on computers running client
   versions of Windows, they’re subject to the inherent limitations of those
   Windows versions. Client versions of Windows are designed primarily to
   be an operating system for a single-user desktop computer rather than
   to function as part of a network. These versions can’t manage a file or
   printer server as efficiently as a real network operating system.
 ✦ If you don’t set up a dedicated network server, someone (hopefully,
   not you) may have to live with the inconvenience of sharing his or her
   computer with the network. With Windows Server, the server comput-
   ers are dedicated to network use so that no one has to put up with this
   inconvenience.
 ✦ Although a peer-to-peer network may have a lower cost per computer
   for smaller networks, the cost difference between peer-to-peer networks
   and Windows Server is less significant in larger networks (say, ten or
   more clients).
 ✦ Peer-to-peer networks don’t work well when your network starts to
   grow. Peer-to-peer servers just don’t have the security or performance
   features required for a growing network.


Windows 7
The current version of Windows is known as Windows 7. It has powerful
peer-to-peer networking features built in, so it’s easy to create a small peer-
to-peer network based on Windows 7.

Vista comes in six editions:

 ✦ Starter: A simplified version that is available only pre-installed on com-
   puter systems from manufacturers such as Dell.
72   Peer-to-Peer Networking with Windows


         ✦ Home Basic: A special version that is available only in certain geo-
           graphic markets such as China, India, and Pakistan. It is not available in
           Europe or the United States.
         ✦ Home Premium: The standard edition for home use. You can use the
           Home Premium edition to build a simple peer-to-peer network, but not
           as part of a domain-based network.
         ✦ Professional: Designed for business users with domain networks.
         ✦ Enterprise: The complete version of Windows 7, which includes all the
           features of Windows 7 Professional and a few extra bells and whistles.
           This edition is available only to large businesses that have volume
           licenses with Microsoft.
         ✦ Ultimate: The retail version of the Enterprise Edition. This version
           includes all of the features of Windows 7 Enterprise but can be pur-
           chased individually by home or small business users.

        Windows 7 provides the following networking features:

         ✦ Built-in file and printer sharing allows you to share files and printers
           with other network users.
         ✦ A Network Setup Wizard automatically sets the most common configura-
           tion options. The wizard eliminates the need to work through multiple
           Properties dialog boxes to configure network settings.
         ✦ An Internet Connection Sharing (ICS) feature allows a Windows com-
           puter to share an Internet connection with other users. The ICS feature
           includes firewall features that protect your network from unauthorized
           access via the Internet connection.
         ✦ A built-in firewall protects the computer when it’s connected to the
           Internet.
         ✦ Simple user account management lets you create multiple users and
           assign passwords.
         ✦ Built-in support for wireless networking makes connecting to a wireless
           network a breeze.
         ✦ Advanced network diagnostics and troubleshooting tools help you find
           and correct networking problems.


        Windows Vista
        The previous version of Windows was known as Windows Vista. Like
        Windows 7, Windows Vista came in several editions. The most popular were:
                       Peer-to-Peer Networking with Windows             73

 ✦ Home Basic: For the simplest home users.                                      Book I
                                                                                Chapter 4
 ✦ Home Premium: Has more advanced features but is still designed for
   home users. Both of the Home versions can be used to create peer-to-




                                                                                Network Operating
   peer networks but can’t be used with domain-based networks.




                                                                                 Understanding
                                                                                    Systems
 ✦ Business: Designed for business users with domain networks.
 ✦ Ultimate: Includes all of the available Windows features.

Most of the improvements made in Windows 7 were in the user interface
rather than in the networking features. As a result, Windows Vista provided
most of the same networking capabilities as Windows 7.


Older Windows versions
Previous versions of Windows also offer peer-to-peer networking features.
The following list summarizes the networking features of the major Windows
releases prior to Windows Vista:

 ✦ Windows XP: This is still a popular version of Windows, even though it
   was replaced by Windows Vista in 2005.
 ✦ Windows Me: The release of Me (short for Millennium Edition) was
   aimed at home users. It provided a Home Networking Wizard to simplify
   the task of configuring a network. It was the last version of Windows that
   was based on the old 16-bit MS-DOS code.
 ✦ Windows 2000 Professional: This is a desktop version of Windows 2000
   Server. It has powerful peer-to-peer networking features similar to those
   found in Windows XP, although they are a bit more difficult to set up.
   It was the first desktop version of Windows that integrated well with
   Active Directory.
 ✦ Windows 98 and Windows 98 Second Edition: These were popular
   upgrades to Windows 95 that enhanced its basic networking features.
 ✦ Windows 95: This was the first 32-bit version of Windows. However, it
   still relied internally on 16-bit MS-DOS code, so it wasn’t a true 32-bit
   operating system. It provided basic peer-to-peer network features, with
   built-in drivers for common network adapters and basic file- and printer-
   sharing features.
 ✦ Windows for Workgroups: This was the first version of Windows to
   support networking without requiring an add-on product. It simplified
   the task of creating NetBIOS-based networks for file and printer sharing.
   However, it had only weak support for TCP/IP.
74         Peer-to-Peer Networking with Windows




                           Workgroups versus domains
     In a Windows network, a domain is a group of        To create a domain, you have to designate a
     server computers that share a common user           server computer as the domain controller and
     account database. A user at a client com-           configure user accounts. Workgroups are
     puter can log in to a domain to access shared       much easier to administer. In fact, you don’t
     resources for any server in the domain. Each        have to do anything to create a workgroup
     domain must have at least one server com-           except decide on the name you want to use.
     puter designated as the domain controller,          Although you can have as many workgroups as
     which is ultimately in charge of the domain.        you want on a peer-to-peer network, most net-
     Most domain networks share this work among          works have just one workgroup. That way, any
     at least two domain controllers, so that if one     computers on the network can share resources
     of the controllers stops working, the network       with any other computer on the network.
     can still function.
                                                         One of the most common mistakes when set-
     A peer-to-peer network can’t have a domain          ting up a peer-to-peer network is misspelling
     because it doesn’t have a dedicated server          the workgroup name on one of the comput-
     computer to act as a domain controller.             ers. For example, suppose you decide that all
     Instead, computers in a peer-to-peer network        the computers should belong to a workgroup
     are grouped in workgroups, which are simply         named MYGROUP. If you accidentally spell
     groups of computers that can share resources        the workgroup name MYGRUOP for one of the
     with each other. Each computer in a workgroup       computers, that computer will be isolated in its
     keeps track of its own user accounts and secu-      own workgroup. If you can’t locate a computer
     rity settings, so no single computer is in charge   on your network, the workgroup name is one of
     of the workgroup.                                   the first things to check.
      Book II
Building a Network
Contents at a Glance
      Chapter 1: Planning a Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77

      Chapter 2: Installing Network Hardware. . . . . . . . . . . . . . . . . . . . . . . . .95

      Chapter 3: Setting Up a Network Server . . . . . . . . . . . . . . . . . . . . . . . .111

      Chapter 4: Configuring Windows Clients. . . . . . . . . . . . . . . . . . . . . . . .121

      Chapter 5: Macintosh Networking . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135

      Chapter 6: Configuring Other Network Features . . . . . . . . . . . . . . . . .141

      Chapter 7: Verifying Your Network Installation . . . . . . . . . . . . . . . . . .151

      Chapter 8: Going Virtual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157
      Chapter 1: Planning a Network
      In This Chapter
      ✓ Making a network plan
      ✓ Taking stock of your computer stock
      ✓ Making sure that you know why you need a network
      ✓ Making the three basic network decisions that you can’t avoid
      ✓ Using a starter kit
      ✓ Looking at a sample network




      O     kay, so you’re convinced that you need to network your computers.
            What now? Do you stop by Computers-R-Us on the way to work, install
      the network before drinking your morning coffee, and expect the network to
      be fully operational by noon?

      I don’t think so.

      Networking your computers is just like any other worthwhile endeavor:
      Doing it right requires a bit of planning. This chapter helps you to think
      through your network before you start spending money. It shows you how
      to come up with a networking plan that’s every bit as good as the plan that a
      network consultant would charge thousands of dollars for. See? This book is
      already saving you money!



Making a Network Plan
      Before you begin any networking project, whether it’s a new network instal-
      lation or an upgrade of an existing network, you should first make a detailed
      plan. If you make technical decisions too quickly, before studying all the
      issues that affect the project, you’ll regret it. You’ll discover too late that a
      key application won’t run over the network, that the network has unaccept-
      ably slow performance, or that key components of the network don’t work
      together.

      Here are some general thoughts to keep in mind while you create your net-
      work plan:
78   Being Purposeful


         ✦ Don’t rush the plan. The most costly networking mistakes are the ones
           that you make before you install the network. Think things through and
           consider alternatives.
         ✦ Write down the network plan. The plan doesn’t have to be a fancy, 500-
           page document. If you want to make it look good, pick up a 1⁄2-inch three-
           ring binder. This binder will be big enough to hold your network plan
           with room to spare.
         ✦ Ask someone else to read your network plan before you buy any-
           thing. Preferably, ask someone who knows more about computers
           than you do.
         ✦ Keep the plan up to date. If you add to the network, dig up the plan,
           dust it off, and update it.

        “The best laid schemes of mice and men gang aft agley, and leave us naught
        but grief and pain for promised joy.” Robert Burns lived a few hundred years
        before computer networks, but his famous words ring true. A network plan
        isn’t chiseled in stone. If you discover that something doesn’t work the way
        you thought it would, that’s okay. Just change your plan.



Being Purposeful
        One of the first steps in planning your network is making sure that you
        understand why you want the network in the first place. Here are some of
        the more common reasons for needing a network, all of them quite valid:

         ✦ My coworker and I exchange files using CDs or flash drives just about
           every day. With a network, it would be easier to trade files.
         ✦ I don’t want to buy everyone a laser printer when I know the one we have
           now just sits there taking up space most of the day. So wouldn’t buying a
           network be better than buying a laser printer for every computer?
         ✦ I want to provide an Internet connection for all my computers. (Many
           networks, especially smaller ones, exist solely for the purpose of sharing
           an Internet connection.)
         ✦ Someone figured out that we’re destroying seven trees a day by printing
           interoffice memos on paper, so we want to save the rainforest by setting
           up an e-mail system.
         ✦ Business is so good that one person typing in orders eight hours each
           day can’t keep up. With a network, I can have two people entering
           orders, and I won’t have to pay overtime to either person.
         ✦ My brother-in-law just put in a network at his office, and I don’t want him
           to think that I’m behind the times.
                                                            Taking Stock         79

        ✦ I already have a network, but it’s so old it may as well be made of kite
          string and tin cans. An improved network will speed up access to shared
          files, provide better security, and be easier to manage.

       Make sure that you identify all the reasons why you think you need a net-
       work and then write them down. Don’t worry about winning the Pulitzer
       Prize for your stunning prose. Just make sure that you write down what you
       expect a network to do for you.

       If you were making a 500-page networking proposal, you’d place the descrip-
       tion of why a network is needed in a tabbed section labeled “Justification.” In
       your 1⁄2-inch network binder, file the description under “Purpose.”
                                                                                          Book II
                                                                                         Chapter 1
       As you consider the reasons why you need a network, you may conclude
       that you don’t need a network after all. That’s okay. You can always use the




                                                                                               Planning a Network
       binder for your stamp collection.



Taking Stock
       One of the most challenging parts of planning a network is figuring out how
       to work with the computers that you already have. In other words, how do
       you get from here to there? Before you can plan how to get “there,” you have
       to know where “here” is. In other words, you have to take a thorough inven-
       tory of your current computers.


       What you need to know
       You need to know the following information about each of your computers:

        ✦ The processor type and, if possible, its clock speed: It would be nice
          if each of your computers had a shiny new i7 Quad Core processor. In
          most cases, though, you find a mixture of computers: some new, some
          old, some borrowed, some blue. You may even find a few archaic pre-
          Pentium computers.
           You can’t usually tell what kind of processor that a computer has just
           by looking at the computer’s case. Most computers, however, display
           the processor type when you turn them on or reboot them. If the infor-
           mation on the startup screen scrolls too quickly for you to read it, try
           pressing the Pause key to freeze the information. After you finish read-
           ing it, press the Pause key again so that your computer can continue
           booting.
        ✦ The size of the hard drive and the arrangement of its partitions: To
          find out the size of your computer’s hard drive in Windows Vista or
          Windows 7, open the Computer window, right-click the drive icon, and
          choose the Properties command from the shortcut menu that appears.
80       Taking Stock


                 Figure 1-1 shows the Properties dialog box for a 922GB hard drive that
                 has about 867GB of free space.




Figure 1-1:
The
Properties
dialog
box for a
disk drive
(Windows
Vista).



                 If your computer has more than one hard drive, Windows lists an icon
                 for each drive in the Computer window. Jot down the size and amount of
                 free space available on each drive.
              ✦ The amount of memory: To find this information in Windows, right-click
                Computer on the Start menu and choose the Properties command. The
                amount of memory on your computer is shown in the dialog box that
                appears. For example, Figure 1-2 shows the System Properties dialog
                box for a computer running Windows 7 with 8GB of RAM.
              ✦ The operating system version: This you can also deduce from the
                System Properties dialog box. For example, the Properties page shown
                in Figure 1-2 indicates that the computer is running Windows 7 Ultimate.
              ✦ What type of network card, if any, is installed in the computer: The
                easiest way to get this information is to right-click Computer on the
                Start menu, choose Manage, click Device Manager, right-click the net-
                work adapter, and choose Properties. For example, Figure 1-3 shows the
                Properties dialog box for the network adapter that’s built into the moth-
                erboard on my computer.
              Taking Stock   81




                                   Book II
                                  Chapter 1

Figure 1-2:




                                        Planning a Network
The
Properties
page for a
Windows 7
system.




Figure 1-3:
The
Properties
page for
a network
adapter.
82      Taking Stock


                 The Device Manager is also useful for tracking down other hardware
                 devices attached to the computer.
              ✦ What network protocols are in use: To determine this in Windows
                Vista, open Control Panel, open Network and Sharing Center, click
                Manage Network Connections, and then right-click the Local Area con-
                nection and choose Properties. In Windows 7, open Control Panel, click
                View Network Status and Tasks, click Change Adapter Settings, then
                right-click the Local Area Connection and choose Properties. The dialog
                box shown in Figure 1-4 appears.




Figure 1-4:
The
Properties
page for a
local area
network
connection.



              ✦ What kind of printer, if any, is attached to the computer: Usually, you
                can tell just by looking at the printer. You can also tell by double-
                clicking the Printers icon in Control Panel.
              ✦ Any other devices connected to the computer: A CD, DVD, or CD-RW
                drive? Scanner? Zip or Jazz drive? Tape drive? Video camera? Battle
                droid? Hot tub?
              ✦ Which driver and installation disks are available: Hopefully, you’ll be
                able to locate the disks or CDs required by hardware devices such as
                the network card, printers, scanners, and so on. If not, you may be able
                to locate the drivers on the Internet.
              ✦ What software is used on the computer: Microsoft Office? AutoCAD?
                QuickBooks? Make a complete list and include version numbers.
                                                                  Taking Stock         83

              Programs that gather information for you
              Gathering information about your computers is a lot of work if you have
              more than a few computers to network. Fortunately, several software pro-
              grams are available that can automatically gather the information for you.
              These programs inspect various aspects of a computer, such as the CPU
              type and speed, amount of RAM, and the size of the computer’s hard drives.
              Then they show the information on the screen and give you the option of
              saving the information to a hard drive file or printing it.

              Windows comes with just such a program, called Microsoft System
              Information. Microsoft System Information gathers and prints information
              about your computer. You can start Microsoft System Information by choos-        Book II
              ing Start➪All Programs➪Accessories➪System Tools➪System Information.             Chapter 1




                                                                                                    Planning a Network
              When you fire up Microsoft System Information, you see a window similar to
              the one shown in Figure 1-5. Initially, Microsoft System Information displays
              basic information about your computer, such as your version of Microsoft
              Windows, the processor type, the amount of memory on the computer,
              and so on. You can obtain more detailed information by clicking Hardware
              Resources, Components, or other categories in the left side of the window.




Figure 1-5:
Let the
System
Information
program
gather the
data you
need.
84   To Dedicate or Not to Dedicate: That Is the Question


To Dedicate or Not to Dedicate: That Is the Question
        One of the most basic questions that a network plan must answer is
        whether the network will have one or more dedicated servers or rely com-
        pletely on peer-to-peer networking. If the only reason for purchasing your
        network is to share a printer and exchange an occasional file, you may not
        need a dedicated server computer. In that case, you can create a peer-to-
        peer network by using the computers that you already have. However, all
        but the smallest networks will benefit from having a separate, dedicated
        server computer.

         ✦ Using a dedicated server computer makes the network faster, easier to
           work with, and more reliable. Consider what happens when the user of
           a server computer, which doubles as a workstation, decides to turn off
           the computer, not realizing that someone else is accessing files on his or
           her hard drive.
         ✦ You don’t necessarily have to use your biggest and fastest computer
           as your server computer. I’ve seen networks where the slowest com-
           puter on the network is the server. This advice is especially true when
           the server is mostly used to share a printer or to store a small number
           of shared files. So if you need to buy a computer for your network, con-
           sider promoting one of your older computers to be the server and using
           the new computer as a client.



Types of Servers
        Assuming that your network will require one or more dedicated servers, you
        should next consider what types of servers the network will need. In some
        cases, a single server computer can fill one or more of these roles. Whenever
        possible, it’s best to limit each server computer to a single server function.


        File servers
        File servers provide centralized disk storage that can be conveniently shared
        by client computers on the network. The most common task of a file server
        is to store shared files and programs. For example, the members of a small
        workgroup can use disk space on a file server to store their Microsoft Office
        documents.

        File servers must ensure that two users don’t try to update the same file at
        the same time. The file servers do this by locking a file while a user updates
        the file so that other users can’t access the file until the first user finishes.
        For document files (for example, word processing or spreadsheet files), the
        whole file is locked. For database files, the lock can be applied just to the
        portion of the file that contains the record or records being updated.
                                                   Types of Servers        85

Print servers
Sharing printers is one of the main reasons that many small networks exist.
Although it isn’t necessary, a server computer can be dedicated for use as
a print server, whose sole purpose is to collect information being sent to a
shared printer by client computers and print it in an orderly fashion.

 ✦ A single computer may double as both a file server and a print server, but
   performance is better if you use separate print and file server computers.
 ✦ With inexpensive inkjet printers running about $100 each, just giving
   each user his or her own printer is tempting. However, you get what
   you pay for. Instead of buying $100 printers for 15 users, you may be          Book II
   better off buying one $1,500 laser printer and sharing it. The $1,500 laser   Chapter 1
   printer will be much faster, will probably produce better-looking output,




                                                                                       Planning a Network
   and will be cheaper to operate.


Web servers
A Web server is a server computer that runs software that enables the
computer to host an Internet Web site. The two most popular Web server
programs are Microsoft’s IIS (Internet Information Services) and Apache, an
open-source Web server managed by the Apache Software Foundation.


Mail servers
A mail server is a server that handles the network’s e-mail needs. It is con-
figured with e-mail server software, such as Microsoft Exchange Server.
Exchange Server is designed to work with Microsoft Outlook, the e-mail
client software that comes with Microsoft Office.

Most mail servers actually do much more than just send and receive elec-
tronic mail. For example, here are some of the features that Exchange Server
offers beyond simple e-mail:

 ✦ Collaboration features that simplify the management of collaborative
   projects.
 ✦ Audio and video conferencing.
 ✦ Chat rooms and instant messaging (IM) services.
 ✦ Microsoft Exchange Forms Designer, which lets you develop customized
   forms for applications, such as vacation requests or purchase orders.


Database servers
A database server is a server computer that runs database software, such as
Microsoft’s SQL Server 2000. Database servers are usually used along with
customized business applications, such as accounting or marketing systems.
86   Choosing a Server Operating System


Choosing a Server Operating System
        If you determine that your network will require one or more dedicated serv-
        ers, the next step is to determine what network operating system those serv-
        ers should use. If possible, all the servers should use the same NOS so that
        you don’t find yourself supporting different operating systems.

        Although you can choose from many network operating systems, from a
        practical point of view, your choices are limited to the following:

         ✦ Windows Server 2003 or 2008
         ✦ Linux or another version of Unix

        For more information, refer to Book I, Chapter 4.



Planning the Infrastructure
        You also need to plan the details of how you will connect the computers in
        the network. This task includes determining which network topology the
        network will use, what type of cable will be used, where the cable will be
        routed, and what other devices (such as repeaters, bridges, hubs, switches,
        and routers) will be needed.

        Although you have many cabling options to choose from, you’ll probably use
        Cat 5e or better UTP for most — if not all — of the desktop client comput-
        ers on the network. However, you have many decisions to make beyond this
        basic choice:

         ✦ Will you use hubs, which are cheaper, or switches, which are faster but
           more expensive?
         ✦ Where will you place workgroup hubs or switches — on a desktop some-
           where within the group or in a central wiring closet?
         ✦ How many client computers will you place on each hub or switch, and
           how many hubs or switches will you need?
         ✦ If you need more than one hub or switch, what type of cabling will you
           use to connect the hubs and switches to one another?

        For more information about network cabling, see Book II, Chapter 2, and
        Book I, Chapter 3.

        If you’re installing new network cable, don’t scrimp on the cable itself.
        Because installing network cable is a labor-intensive task, the cost of the
        cable itself is a small part of the total cable installation cost. And if you
        spend a little extra to install higher-grade cable now, you won’t have to
        replace the cable in a few years when it’s time to upgrade the network.
                                                             Drawing Diagrams          87

Drawing Diagrams
              One of the most helpful techniques for creating a network plan is to draw a
              picture of it. The diagram can be a detailed floor plan, showing the actual
              location of each network component. This type of diagram is sometimes
              called a physical map. If you prefer, the diagram can be a logical map, which
              is more abstract and Picasso-like. Any time you change the network layout,
              update the diagram. Also include a detailed description of the change, the
              date that the change was made, and the reason for the change.

              You can diagram very small networks on the back of a napkin, but if the net-
              work has more than a few computers, you’ll want to use a drawing program         Book II
              to help you create the diagram. One of the best programs for this purpose       Chapter 1
              is Microsoft Visio, shown in Figure 1-6. Here’s a rundown of some of the fea-




                                                                                                    Planning a Network
              tures that make Visio so useful:




Figure 1-6:
Using Visio
to draw a
network
diagram.



               ✦ Smart shapes and connectors maintain the connections you’ve drawn
                 between network components, even if you rearrange the layout of the
                 components on the page.
               ✦ Stencils provide dozens of useful shapes for common network
                 components — not just for client and server computers, but for rout-
                 ers, hubs, switches, and just about anything else you can imagine. If
88   Sample Network Plans


            you’re really picky about the diagrams, you can even purchase stencil
            sets that have accurate drawings of specific devices, such as Cisco
            routers or IBM mainframe computers.
         ✦ You can add information to each computer or device in the diagram, such
           as the serial number or physical location. Then, you can quickly print an
           inventory that lists this information for each device in the diagram.
         ✦ You can easily create large diagrams that span multiple pages.



Sample Network Plans
        In what’s left of this chapter, I present some network plans that are drawn
        from real-life situations. These examples illustrate many of the network
        design issues I’ve covered so far in this chapter. The stories you’re about to
        read are true. The names have been changed to protect the innocent.


        Building a small network: California
        Sport Surface, Inc.
        California Sport Surface, Inc. (CSS) is a small company specializing in the
        installation of outdoor sports surfaces, such as tennis courts, running tracks,
        and football fields. CSS has an administrative staff of just four employees
        who work out of a home office. The company currently has three computers:

         ✦ A brand-new Dell desktop computer running Windows 7 Basic, shared
           by the president (Mark) and vice president (Julie) to prepare proposals
           and marketing brochures, to handle correspondence, and to do other
           miscellaneous chores. This computer has a built-in gigabit Ethernet net-
           work port.
         ✦ An older Gateway computer running Windows XP Home Edition, used
           by the bookkeeper (Erin), who uses QuickBooks to handle the com-
           pany’s accounting needs. This computer has a built-in 10/100 Mbps
           Ethernet port.
         ✦ A notebook that runs Windows Vista, used by the company’s chief engi-
           neer (Daniel), who often takes it to job sites to help with engineering
           needs. This computer has a built-in 10/100 Mbps Ethernet port.

        The company owns just one printer, a moderately priced inkjet printer that’s
        connected to Erin’s computer. The computers aren’t networked, so when-
        ever Mark, Julie, or Daniel needs to print something, the file must be copied
        to a flash drive and given to Erin, who then prints the document. The com-
        puter shared by Mark and Julie is connected to the Internet via a residential
        DSL connection.
                                                        Sample Network Plans          89

              The company wants to install a network to support these three computers.
              Here are the primary goals of the network:

               ✦ Provide shared access to the printer so that users don’t have to
                 exchange data on flash drives to print their documents.
               ✦ Provide shared access to the Internet connection so that users can
                 access the Internet from any of the computers.
               ✦ Allow for the addition of another desktop computer, which the company
                 expects to purchase within the next six months, and potentially another
                 notebook computer. (If business is good, the company hopes to hire
                 another engineer.)
                                                                                               Book II
               ✦ The network should be intuitive to the users and shouldn’t require           Chapter 1
                 extensive upkeep.




                                                                                                    Planning a Network
              CSS’s networking needs can be met with the simple peer-to-peer network dia-
              grammed in Figure 1-7. Here’s what the network requires:

               ✦ The network needs a combination DSL router and four-port gigabit
                 network switch. The company may outgrow this device when it adds a
                 laptop, but if and when that happens, another 4- or 8-port switch can be
                 added at that time.
               ✦ The firewall features of the DSL router will need to be enabled to protect
                 the network from Internet hackers.
               ✦ File and printer sharing will need to be activated on Erin’s computer,
                 and the printer will need to be shared.




                                                         Printer
                   Mark/Julie               Erin



                               DSL router/             DSL modem
Figure 1-7:              gigabit network switch
California
Sport
Surface’s
new peer-                                                          The Internet
to-peer
network.        Daniel
90   Sample Network Plans


        Connecting two networks: Creative
        Course Development, Inc.
        Creative Course Development, Inc. (CCD) is a small educational publisher
        located in central California that specializes in integrated math and sci-
        ence curriculum for primary and secondary grades. It publishes a variety of
        course materials, including textbooks, puzzle books, and CD-ROM software.

        CCD leases two office buildings that are adjacent to each other, separated
        only by a small courtyard. The creative staff, which consists of a dozen writ-
        ers and educators, works in Building A. The sales, marketing, and adminis-
        trative staff, which consists of six employees, works in Building B.

        The creative staff (Building A) has a dozen relatively new personal comput-
        ers, all running Windows Vista Business Edition, and a server computer
        running Windows 2003 Server. These computers are networked via a single
        24-port gigabit network switch. A fractional T1 line that’s connected to the
        network through a small Cisco router provides Internet access.

        The sales, marketing, and administrative staff (Building B) has a hodge-
        podge of computers, some running Windows Vista but most running
        Windows XP. They have a small Windows 2003 server that meets their
        needs. The older computers have 10/100BaseT network interfaces; the
        newer ones have gigabit interfaces. However, the computers are all con-
        nected to a 10/100 Mbps Ethernet switch with 12 ports. Internet access is
        provided by an ISDN connection.

        Both groups are happy with their computers and networks. The problem
        is that the networks can’t communicate with each other. For example, the
        creative team in Building A prepares weekly product-development status
        reports to share with the Administrative staff in Building B, and they fre-
        quently go to the other building to look into important sales trends.

        Although several solutions to this problem exist, the easiest is to bridge the
        networks with a pair of wireless switches. To do this, CCD will purchase
        two wireless access points. One will be plugged into the gigabit switch in
        Building A, and the other will be plugged into the switch in Building B. After
        the access points are configured, the two networks will function as a single
        network. Figure 1-8 shows a logical diagram for the completed network.

        Although the wireless solution to this problem sounds simple, a number of
        complications still need to be dealt with. Specifically:

         ✦ Depending on the environment, the wireless access points may have
           trouble establishing a link between the buildings. It may be necessary
           to locate the devices on the roof. In that case, CCD will have to spend a
           little extra money for weatherproof enclosures.
                                                                  Sample Network Plans                    91

                 Dave Y.   Brenda M. Deborah Q.       Julie D.      Chris E.    Alice M.




                   24-port Gigabit Switch                                                      The Internet
                                                                      Cisco 1700   T1


                                                                                                                Book II
                                                                                                               Chapter 1
                                                                                                Building A




                                                                                                                     Planning a Network
               Emily D.    Sarah L.    Toby S.            Juan S.     Richard O.    Elias H.

                                                          Wireless Access Point




                                                                      Wireless Access Point

                            Building B
Figure 1-8:                                                               12-port 10/100 Mbps Switch
Creative
Course
Develop-
ment’s
wireless
network
solution.
                           Andrew T.        Bill B.   Shawna S.      Maria L.      Erin C.      William H.



              ✦ Before the networks were connected, each network had its own DHCP
                server to assign IP addresses to users as needed. Unfortunately, both
                DHCP servers have the same local IP address (192.168.0.1). When the net-
                works are combined, one of these DHCP servers will have to be disabled.
              ✦ In addition, both networks had their own Internet connections. With the
                networks bridged, CCD can eliminate the ISDN connection altogether.
                Users in both buildings can get their Internet access via the shared T1
                connection.
92   Sample Network Plans


         ✦ The network administrator will also have to determine how to handle
           directory services for the network. Previously, each network had its own
           domain. With the networks bridged, CCD may opt to keep these domains
           separate, or it may decide to merge them into a single domain. (Doing so
           will require considerable work, so the company will probably leave the
           domains separate.)


        Improving network performance: DCH Accounting
        DCH Accounting is an accounting firm that has grown in two years from
        15 employees to 35, all located in one building. Here’s the lowdown on the
        existing network:

         ✦ The network consists of 35 client computers and three servers running
           Windows 2003 Server.
         ✦ The 35 client computers run a variety of Windows operating systems.
           About a third (a total of 11) run Windows Vista Professional. The rest
           run Windows XP Professional. None of the computers run Windows 7.
         ✦ The Windows Vista computers all have gigabit Ethernet cards. The older
           computers have 10/100 Mbps cards.
         ✦ The server computers are somewhat older computers that have 10/100
           Mbps network interfaces.
         ✦ All the offices in the building are wired with Category 5e wiring to a
           central wiring closet, where a small equipment rack holds two 24-port
           10/100 switches.
         ✦ Internet access is provided through a T1 connection with a Cisco 1700
           router.

        Lately, network performance has been noticeably slow, particularly
        Internet access and large file transfers between client computers and the
        servers. Users have started to complain that sometimes the network seems
        to crawl.

        The problem is most likely that the network has outgrown the old
        10/100BaseT switches. All network traffic must flow through them, and
        they’re limited to the speed of 100 Mbps. As a result, the new computers
        with the gigabit Ethernet cards are connecting to the network at 100 Mbps.

        The performance of this network can be dramatically improved in two steps.
        The first step is to replace the 10/100 Mbps network interface cards in the
        three servers with gigabit cards (or, better yet, replace the servers with
        newer models). Second, add a 24-port gigabit switch to the equipment rack.
        The equipment rack can be rewired, as shown in Figure 1-9.
DCH


network.
switched
Figure 1-9:

Accounting’s
                                                The Internet


                                                               Servers
                 Cisco 1700

                                24-port Gigabit
                                Switch
    Gigabit




10/100 Mbps                     24-port 10/100 Switch
                                                                         Sample Network Plans




                                24-port 10/100 Switch
10/100 Mbps
                                                                         93




                                     Book II




               Planning a Network
                                    Chapter 1
94   Sample Network Plans


        1. Connect the servers, the Cisco router, and the gigabit clients to the
            new gigabit switch. This will use 15 of the 24 ports.
        2. Connect the two 10/100 switches to the new gigabit switch. This will
            use two more ports, leaving 7 ports for future growth.
        3. Divide the remaining clients between the two 10/100 switches. Each
            switch will have 12 computers connected.

        This arrangement connects all the gigabit clients to gigabit switch ports and
        100 Mbps clients to 100 Mbps switch ports.

        For even better performance, DCH can simply replace both switches with
        24-port gigabit switches.
       Chapter 2: Installing
       Network Hardware
       In This Chapter
       ✓ Installing network interface cards
       ✓ Installing network cable
       ✓ Attaching cable connectors
       ✓ Figuring out pinouts for twisted-pair cabling
       ✓ Building a crossover cable
       ✓ Installing switches




       A     fter you have your network planned out, then comes the fun of actu-
             ally putting everything together. In this chapter, I describe some of
       the important details for installing network hardware, including cables,
       switches, network interface cards, and professional touches, such as patch
       panels.



Installing a Network Interface Card
       To connect a computer to your network, the computer must have a network
       interface. Virtually all computers sold in the last 10 years or so have a net-
       work interface built-in on the motherboard. However, you may still encoun-
       ter the occasional older computer that doesn’t have a built-in network
       interface. In that case, you must install a network interface card to enable
       the computer for your network. Installing a network interface card is a man-
       ageable task, but you have to be willing to roll up your sleeves.

       If you’ve installed one adapter card, you’ve installed them all. In other
       words, installing a network interface card is just like installing a modem, a
       new video controller card, a sound card, or any other type of card. If you’ve
       ever installed one of these cards, you can probably install a network inter-
       face card blindfolded.

       Here’s a step-by-step procedure for installing a network interface card:
96       Installing a Network Interface Card


              1. Gather up the network card and the driver disks. While you’re at it,
                 get your Windows installation CD just in case.
              2. Shut down Windows and then turn off the computer and unplug it.
                 Never work in your computer’s insides with the power on or the power
                 cord plugged in!
              3. Remove the cover from your computer.
                 Figure 2-1 shows the screws that you must typically remove in order to
                 open the cover. Put the screws someplace where they won’t wander off.



                                       Remove these screws




Figure 2-1:
Removing
your
computer’s
cover.



                 Note that if you have a name-brand computer such as a Dell or a
                 Compaq, opening the cover may be trickier than just removing a few
                 screws. You may need to consult the owner’s manual that came with the
                 computer to find out how to open the case.
              4. Find an unused expansion slot inside the computer.
                 The expansion slots are lined up in a neat row near the back of the com-
                 puter; you can’t miss ’em. Any computer less than five years old should
                 have at least two or three slots known as PCI slots.
              5. When you find a slot that doesn’t have a card in it, remove the metal
                 slot protector from the back of the computer’s chassis.
                 If a small retaining screw holds the slot protector in place, remove the
                 screw and keep it in a safe place. Then pull the slot protector out and
                 put the slot protector in a box with all your other old slot protectors.
                 (After a while, you collect a whole bunch of slot protectors. Keep them
                 as souvenirs or Christmas tree ornaments.)
              6. Insert the network interface card into the slot.
                                           Installing Twisted-Pair Cable          97

           Line up the connectors on the bottom of the card with the connec-
           tors in the expansion slot and then press the card straight down.
           Sometimes you have to press uncomfortably hard to get the card to
           slide into the slot.
       7. Secure the network interface card with the screw that you removed in
           Step 5.
       8. Put the computer’s case back together.
           Watch out for the loose cables inside the computer; you don’t want to
           pinch them with the case as you slide it back on. Secure the case with
           the screws that you removed in Step 3.
                                                                                         Book II
       9. Plug in the computer and turn it back on.                                     Chapter 2

       If you’re using a Plug and Play card with Windows, the card is automatically




                                                                                           Installing Network
       configured after you start the computer again. If you’re working with an




                                                                                                Hardware
       older computer or an older network interface card, you may need to run an
       additional software installation program. See the installation instructions
       that come with the network interface card for details.



Installing Twisted-Pair Cable
       Most Ethernet networks are built using twisted-pair cable, which resembles
       phone cable but isn’t the same. Twisted-pair cable is sometimes called UTP.
       For more information about the general characteristics of twisted-pair cable,
       refer to Book I, Chapter 3.

       In the following sections, you find out what you need to know in order to
       select and install twisted-pair cable.


       Cable categories
       Twisted-pair cable comes in various grades called Categories. These
       Categories are specified by the ANSI/EIA standard 568. (ANSI stands for
       American National Standards Institute; EIA stands for Electronic Industries
       Association.) The standards indicate the data capacity, also known as the
       bandwidth, of the cable. Table 2-1 lists the various Categories of twisted-
       pair cable.

       Although higher-Category cables are more expensive than lower-Category
       cables, the real cost of installing Ethernet cabling is the labor required to
       actually pull the cables through the walls. You should never install any-
       thing less than Category 5 cable. And if at all possible, you should invest in
       Category 5e (the e stands for enhanced) or even Category 6 cable to allow
       for future upgrades to your network.
98   Installing Twisted-Pair Cable


        If you want to sound like you know what you’re talking about, say “Cat 5”
        instead of “Category 5.”



           Table 2-1                 Twisted-Pair Cable Categories
          Category       Maximum Data Rate               Intended Use
          1              1 Mbps                          Voice only
          2              4 Mbps                          4 Mbps Token Ring
          3              16 Mbps                         10BaseT Ethernet
          4              20 Mbps                         16 Mbps Token Ring
          5              100 Mbps (2 pair)               100BaseT Ethernet
                         1,000 Mbps (4 pair)             Gigabit Ethernet
          5e             1,000 Mbps (2 pair)             Gigabit Ethernet
          6              1,000 Mbps (2 pair)             Gigabit Ethernet
          6a             10,000 Mbps                     10 gigabit (experimental)
          7              10,000 Mbps                     10 gigabit (experimental)



        What’s with the pairs?
        Most twisted-pair cable has four pairs of wires, for a total of eight wires.
        Standard Ethernet actually uses only two of the pairs, so the other two pairs
        are unused. You may be tempted to save money by purchasing cable with
        just two pairs of wires, but that’s a bad idea. If a network cable develops
        a problem, you can sometimes fix it by switching over to one of the extra
        pairs. But if you try to carry a separate connection over the extra pairs, elec-
        trical interference will prevent the signals from getting through.

        You may also be tempted to use the extra pairs for some other purpose,
        such as for a voice line. Don’t. The electrical noise generated by voice sig-
        nals in the extra wires can interfere with your network.


        To shield or not to shield
        Unshielded twisted-pair cable, or UTP, is designed for normal office environ-
        ments. When you use UTP cable, you must be careful not to route cable
        close to fluorescent light fixtures, air conditioners, or electric motors (such
        as automatic door motors or elevator motors). UTP is the least expensive
        type of cable.
                                   Installing Twisted-Pair Cable          99

In environments that have a lot of electrical interference, such as facto-
ries, you may want to use shielded twisted-pair cable, also known as STP.
Because STP can be as much as three times more expensive than regular
UTP, you won’t want to use STP unless you have to. With a little care, UTP
can withstand the amount of electrical interference found in a normal
office environment.

Most STP cable is shielded by a layer of aluminum foil. For buildings with
unusually high amounts of electrical interference, you can use more expen-
sive, braided copper shielding for even more protection.


When to use plenum cable                                                          Book II
                                                                                 Chapter 2
The outer sheath of both shielded and unshielded twisted-pair cable comes
in two varieties: PVC and Plenum. PVC cable is the most common and least




                                                                                    Installing Network
expensive type. Plenum cable is a special type of fire-retardant cable that is




                                                                                         Hardware
designed for use in the plenum space of a building. Plenum cable has a spe-
cial Teflon coating that not only resists heat, but also gives off fewer toxic
fumes if it does burn. Unfortunately, plenum cable costs more than twice as
much as ordinary PVC cable.

Most local building codes require that you use plenum cable whenever the
wiring is installed within the plenum space of the building. The plenum space
is a compartment that’s part of the building’s air distribution system and is
usually the space above a suspended ceiling or under a raised floor.

Note that the area above a suspended ceiling is not a plenum space if both
the delivery and return lines of the air-conditioning and heating system are
ducted. Plenum cable is required only if the air-conditioning and heating
system are not ducted. When in doubt, it’s best to have the local inspector
look at your facility before you install cable.


Sometimes solid, sometimes stranded
The actual copper wire that composes the cable comes in two varieties:
solid and stranded. Your network will have some of each.

 ✦ In stranded cable, each conductor is made from a bunch of very small
   wires that are twisted together. Stranded cable is more flexible than
   solid cable, so it doesn’t break as easily. However, stranded cable is
   more expensive than solid cable and isn’t very good at transmitting sig-
   nals over long distances. Stranded cable is best used for patch cables,
   such as the cable used to connect a computer to a wall jack or the cable
   used to connect patch panels to hubs and switches.
100   Installing Twisted-Pair Cable


             Strictly speaking, the cable that connects your computer to the wall jack
             is called a station cable — not a patch cable. Patch cables are used in the
             wiring closet, usually to connect patch panels to switches.
          ✦ In solid cable, each conductor is a single solid strand of wire. Solid
            cable is less expensive than stranded cable and carries signals farther,
            but it isn’t very flexible. If you bend it too many times, it will break. Solid
            cable is usually used for permanent wiring within the walls and ceilings
            of a building.


         Installation guidelines
         The hardest part about installing network cable is the physical task of pulling
         the cable through ceilings, walls, and floors. This job is just tricky enough that
         I recommend that you don’t attempt it yourself except for small offices. For
         large jobs, hire a professional cable installer. You may even want to hire a pro-
         fessional for small jobs if the ceiling and wall spaces are difficult to access.

         Here are some general pointers to keep in mind if you decide to install cable
         yourself:

          ✦ You can purchase twisted-pair cable in prefabricated lengths, such as 50
            feet, 75 feet, or 100 feet. You can also special-order prefabricated cables
            in any length you need. However, attaching connectors to bulk cable
            isn’t that difficult. I recommend that you use prefabricated cables only
            for very small networks and only when you don’t need to route the cable
            through walls or ceilings.
          ✦ Always use a bit more cable than you need, especially if you’re running
            cable through walls. For example, when you run a cable up a wall, leave
            a few feet of slack in the ceiling above the wall. That way, you’ll have
            plenty of cable if you need to make a repair later on.
          ✦ When running cable, avoid sources of interference, such as fluorescent
            lights, big motors, X-ray machines, and so on. The most common source
            of interference for cables that are run behind fake ceiling panels are fluo-
            rescent lights; be sure to give light fixtures a wide berth as you run your
            cable. Three feet should do it.
          ✦ The maximum allowable cable length between the hub and the com-
            puter is 100 meters (about 328 feet).
          ✦ If you must run cable across the floor where people walk, cover the
            cable so that no one trips over it. Inexpensive cable protectors are avail-
            able at most hardware stores.
          ✦ When running cables through walls, label each cable at both ends. Most
            electrical supply stores carry pads of cable labels that are perfect for
            the job. These pads contain 50 sheets or so of precut labels with letters
                                    Installing Twisted-Pair Cable        101

    and numbers. They look much more professional than wrapping a loop
    of masking tape around the cable and writing on the tape with a marker.
    Or, if you want to scrimp, you can just buy a permanent marker and
    write directly on the cable.
 ✦ When several cables come together, tie them with plastic cable ties.
   Avoid masking tape if you can; the tape doesn’t last, but the sticky glue
   stuff does. It’s a mess a year later. Cable ties are available at electrical
   supply stores.
 ✦ Cable ties have all sorts of useful purposes. Once on a backpacking trip,
   I used a pair of cable ties to attach an unsuspecting buddy’s hat to a
   high tree limb. He wasn’t impressed with my innovative use of the cable         Book II
   ties, but my other hiking companions were.                                     Chapter 2

 ✦ When you run cable above suspended ceiling panels, use cable ties,




                                                                                     Installing Network
   hooks, or clamps to secure the cable to the actual ceiling or to the metal




                                                                                          Hardware
   frame that supports the ceiling tiles. Don’t just lay the cable on top of
   the tiles.


Getting the tools that you need
Of course, to do a job right, you must have the right tools.

Start with a basic set of computer tools, which you can get for about $15
from any computer store or large office-supply store. These kits include the
right screwdrivers and socket wrenches to open up your computers and
insert adapter cards. (If you don’t have a computer toolkit, make sure that
you have several flat-head and Phillips screwdrivers of various sizes.)

If all your computers are in the same room and you’re going to run the
cables along the floor and you’re using prefabricated cables, the computer
tool kit should contain everything that you need.

If you’re using bulk cable and plan on attaching your own connectors, you
need the following tools in addition to the tools that come with the basic
computer tool kit:

 ✦ Wire cutters: You need big ones for thinnet cable; smaller ones are okay
   for 10BaseT cable. If you’re using yellow cable, you need the Jaws of Life.
 ✦ Crimp tool: You need the crimp tool to attach the connectors to the
   cable. Don’t use a cheap $10 crimp tool. A good one will cost $100 and
   will save you many headaches in the long run. Remember this adage:
   When you crimp, you mustn’t scrimp.
 ✦ Wire stripper: You need this only if the crimp tool doesn’t include a
   wire stripper.
102   Installing Twisted-Pair Cable


         If you plan on running cables through walls, you need these additional tools:

          ✦ A hammer.
          ✦ A bell.
          ✦ A song to sing. Just kidding about these last two.
          ✦ A keyhole saw. This is useful if you plan on cutting holes through walls
            to route your cable.
          ✦ A flashlight.
          ✦ A ladder.
          ✦ Someone to hold the ladder.
          ✦ Possibly a fish tape. A fish tape is a coiled-up length of stiff metal tape.
            To use it, you feed the tape into one wall opening and fish it toward the
            other opening, where a partner is ready to grab it when the tape arrives.
            Next, your partner attaches the cable to the fish tape and yells some-
            thing like “Let ’er rip!” or “Bombs away!” Then you reel in the fish tape
            and the cable along with it. (You can find fish tape in the electrical sec-
            tion of most well-stocked hardware stores.)

         If you plan on routing cable through a concrete subfloor, you need to rent a
         jackhammer and a backhoe and hire someone to hold a yellow flag while you
         work.


         Pinouts for twisted-pair cables
         Each pair of wires in a twisted-pair cable is one of four colors: orange, green,
         blue, or brown. The two wires that make up each pair are complementary:
         One is a solid color, the other is white with a stripe of the corresponding
         color. For example, the orange pair has an orange wire and a white wire with
         an orange stripe. Likewise, the blue pair has a blue wire and a white wire
         with a blue stripe.

         When you attach a twisted-pair cable to a modular connector or jack, you
         must match up the right wires to the right pins. You can use several differ-
         ent standards to wire the connectors. To confuse matters, you can use one
         of the two popular standard ways of hooking up the wires. One is known as
         EIA/TIA 568A; the other is EIA/TIA 568B, also known as AT&T 258A. Table 2-2
         shows both wiring schemes.

         It doesn’t matter which of these wiring schemes you use, but pick one and
         stick with it. If you use one wiring standard on one end of a cable and the
         other standard on the other end, the cable won’t work.
                                    Installing Twisted-Pair Cable          103

  Table 2-2            Pin Connections for Twisted-Pair Cable
  Pin Number       Function           EIA/TIA 568A          EIA/TIA 568B
                                                            AT&T 258A
  Pin 1            Transmit +         White/green           White/orange
  Pin 2            Transmit –         Green                 Orange
  Pin 3            Receive +          White/orange          White/green
  Pin 4            Unused             Blue                  Blue
  Pin 5            Unused             White/blue            White/blue
  Pin 6            Receive –          Orange                Green
                                                                                    Book II
  Pin 7            Unused             White/brown           White/brown            Chapter 2
  Pin 8            Unused             Brown                 Brown




                                                                                      Installing Network
                                                                                           Hardware
10BaseT and 100BaseT actually use only two of the four pairs, connected to
pins 1, 2, 3, and 6. One pair is used to transmit data, and the other is used to
receive data. The only difference between the two wiring standards is which
pair is used to transmit data and which pair is used to receive data. In the
EIA/TIA 568A standard, the green pair is used to transmit and the orange
pair is used to receive. In the EIA/TIA 568B and AT&T 258A standards, the
orange pair is used to transmit and the green pair to receive.

If you want, you can get away with connecting only pins 1, 2, 3, and 6.
However, I suggest that you connect all four pairs as indicated in Table 2-2.


Attaching RJ-45 connectors
RJ-45 connectors for twisted-pair cables aren’t too difficult to attach if you
have the right crimping tool. The trick is in both making sure that you attach
each wire to the correct pin and pressing the tool hard enough to ensure a
good connection.

Here’s the procedure for attaching an RJ-45 connector:

1. Cut the end of the cable to the desired length.
    Make sure that you make a square cut — not a diagonal cut.
2. Insert the cable into the stripper portion of the crimp tool so that the
    end of the cable is against the stop.
    Squeeze the handles and slowly pull the cable out, keeping it square.
    This strips off the correct length of outer insulation without puncturing
    the insulation on the inner wires.
104      Installing Twisted-Pair Cable


              3. Arrange the wires so that they lay flat and line up according to
                  Table 2-2.
                  You’ll have to play with the wires a little bit to get them to lay out in the
                  right sequence.
              4. Slide the wires into the pinholes on the connector.
                  Double-check to make sure that all the wires slipped into the correct
                  pinholes.
              5. Insert the plug and wire into the crimping portion of the tool and then
                  squeeze the handles to crimp the plug.
                  Squeeze it tight!
              6. Remove the plug from the tool and double-check the connection.
                  You’re done!

              Here are a few other points to remember when dealing with RJ-45 connec-
              tors and twisted-pair cable:

              ✦ The pins on the RJ-45 connectors aren’t numbered, but you can tell
                which is pin 1 by holding the connector so that the metal conductors
                are facing up, as shown in Figure 2-2. Pin 1 is on the left.




                        67   8
                  12345                        Pin connections:
                                               Pin 1 - White/Orange
Figure 2-2:                                    Pin 2 - Orange/White
Attaching                                      Pin 3 - White/Green
                                               Pin 6 - Green/White
an RJ-45
connector
to twisted-
pair cable.



              ✦ Some people wire 10baseT cable differently — using the green and white
                pair for pins 1 and 2 and the orange and white pair for pins 3 and 6. This
                doesn’t affect the operation of the network (the network is color-blind),
                as long as the connectors on both ends of the cable are wired the same!
               ✦ If you’re installing cable for a Fast Ethernet system, you should be extra
                 careful to follow the rules of Category-5 cabling. That means, among other
                 things, making sure that you use Category-5 components throughout.
                                     Installing Twisted-Pair Cable      105

    The cable and all the connectors must be up to Category-5 specs. When
    you attach the connectors, don’t untwist more than 1⁄2 inch of cable.
    And don’t try to stretch the cable runs beyond the 100-meter maximum.
    When in doubt, have cable for a 100 Mbps Ethernet system professionally
    installed.


Crossover cables
A crossover cable is a cable that you can use to directly connect two devices
without a switch. You can use a crossover cable to connect two computers
directly to each other, but crossover cables are more often used to daisy-
chain hubs and switches to each other.
                                                                                   Book II
                                                                                  Chapter 2
If you want to create your own crossover cable, you have to reverse the
wires on one end of the cable, as shown in Table 2-3. This table shows how




                                                                                     Installing Network
you should wire both ends of the cable to create a crossover cable. Connect




                                                                                          Hardware
one of the ends according to the Connector A column and the other accord-
ing to the Connector B column.

Note that you don’t need to use a crossover cable if one of the switches or
hubs that you want to connect has a crossover port, usually labeled Uplink.
If the switch has an Uplink port, you can daisy-chain it by using a normal net-
work cable. For more information about daisy-chaining hubs and switches,
see the section, “Installing Switches,” later in this chapter.



  Table 2-3                    Creating a Crossover Cable
  Pin                 Connector A                  Connector B
  Pin 1               White/green                  White/orange
  Pin 2               Green                        Orange
  Pin 3               White/orange                 White/green
  Pin 4               Blue                         Blue
  Pin 5               White/blue                   White/blue
  Pin 6               Orange                       Green
  Pin 7               White/brown                  White/brown
  Pin 8               Brown                        Brown



Wall jacks and patch panels
If you want, you can run a single length of cable from a network switch in
a wiring closet through a hole in the wall, up the wall to the space above
the ceiling, through the ceiling space to the wall in an office, down the
106      Installing Twisted-Pair Cable


              wall, through a hole, and all the way to a desktop computer. That’s not a
              good idea, however, for a variety of reasons. For one, every time someone
              moves the computer or even cleans behind it, the cable will get moved a
              little bit. Eventually, the connection will fail, and the RJ-45 plug will have
              to be replaced. Then the cables in the wiring closet will quickly become a
              tangled mess.

              The alternative is to put a wall jack in the wall at the user’s end of the cable
              and connect the other end of the cable to a patch panel. Then, the cable
              itself is completely contained within the walls and ceiling spaces. To con-
              nect a computer to the network, you plug one end of a patch cable (prop-
              erly called a station cable) into the wall jack and plug the other end into the
              computer’s network interface. In the wiring closet, you use a patch cable
              to connect the wall jack to the network switch. Figure 2-3 shows how this
              arrangement works.



                                                                         Patch panel




                                                                             Switch




Figure 2-3:
Using
wall jacks
and patch                        Modular
panels.                          wall jacks



              Connecting a twisted-pair cable to a wall jack or a patch panel is similar to
              connecting it to an RJ-45 plug. However, you don’t usually need any special
              tools. Instead, the back of the jack has a set of slots that you lay each wire
                                                 Installing Coaxial Cable        107

       across. You then snap a removable cap over the top of the slots and press
       it down. This forces the wires into the slots, where little metal blades pierce
       the insulation and establish the electrical contact.

       When you connect the wire to a jack or patch panel, be sure to untwist as
       little of the wire as possible. If you untwist too much of the wire, the signals
       that pass through the wire may become unreliable.



Installing Coaxial Cable
       Although twisted-pair cable is by far the most commonly used type of net-           Book II
       working cable, some networks still rely on old-fashioned coaxial cable, usu-       Chapter 2
       ally called thinnet or sometimes BNC cable because of the type of connectors
       used on each end of the cable.




                                                                                             Installing Network
                                                                                                  Hardware
       Here are some salient points about working with coaxial cable:

        ✦ You attach thinnet to the network interface card by using a goofy twist-
          on connector called a BNC connector. You can purchase preassembled
          cables with BNC connectors already attached in lengths of 25 or 50 feet,
          or you can buy bulk cable on a big spool and attach the connectors
          yourself by using a special tool. (I suggest buying preassembled cables.
          Attaching connectors to bulk coaxial cable can be tricky.)
        ✦ With coaxial cables, you run cable from computer to computer until all
          the computers are chained together. At each computer, use a T connec-
          tor to connect two cables to the network interface card.
        ✦ A special plug called a terminator is required at each end of a series of
          thinnet cables. The terminator prevents data from spilling out the end of
          the cable and staining the carpet.
        ✦ The cables strung end-to-end from one terminator to the other are col-
          lectively called a segment. The maximum length of a thinnet segment
          is about 200 meters (actually, 185 meters). You can connect as many
          as 30 computers on one segment. To span a distance greater than 185
          meters or to connect more than 30 computers, you must use two or
          more segments with a funky device called a repeater to connect each
          segment.
        ✦ Although Ethernet coaxial cable resembles TV coaxial cable, the two
          types of cable aren’t interchangeable. Don’t try to cut costs by wiring
          your network with cheap TV cable.
108      Attaching a BNC Connector to Coaxial Cable


Attaching a BNC Connector to Coaxial Cable
              Properly connecting a BNC connector to coaxial cable is an acquired skill.
              You need two tools — a wire stripper that can cut through the various layers
              of the coaxial cable at just the right location and a crimping tool that crimps
              the connector tightly to the cable after you get the connector into position.
              BNC connectors have three separate pieces, as shown in Figure 2-4.

              Here’s the procedure, in case you ignore my advice and try to attach the
              connectors yourself:

              1. Slide the hollow tube portion of the connector (lovingly called the fer-
                  rule) over the cable.
                  Let it slide back a few feet to get it out of the way.
              2. Cut the end of the cable off cleanly.
              3. Use the stripping tool to strip the cable.
                  Strip the outer jacket back 1⁄2 inch from the end of the cable; strip the
                  braided shield back 1⁄4 inch from the end; and then strip the inner insula-
                  tion back 3⁄16 inch from the end.



                     Connector body




                                 Center pin



                                                         Ferrule

Figure 2-4:
Attaching
a BNC
connector             Properly stripped cable
to coaxial
cable.



              4. Insert the solid center conductor into the center pin.
                  Slide the center pin down until it covers the inner insulation.
                                               Daisy-Chaining Switches         109

       5. Use the crimping tool to crimp the center pin.
       6. Slide the connector body over the center pin and inner insulation but
           under the braided shield.
           After you push the body back far enough, the center pin clicks into place.
       7. Now slide the ferrule forward until it touches the connector body.
           Crimp it with the crimping tool.

       Don’t get sucked into the trap of trying to use easy “screw-on” connectors.
       They aren’t very reliable.
                                                                                           Book II
                                                                                          Chapter 2
Installing Switches




                                                                                             Installing Network
       Setting up a network switch is remarkably simple. In fact, you need to know




                                                                                                  Hardware
       only a few details:

        ✦ Installing a switch is usually very simple. Just plug in the power cord
          and then plug in patch cables to connect the network.
        ✦ Each port on the switch has an RJ-45 jack and a single LED indicator
          labeled Link that lights up when a connection has been established on
          the port. If you plug one end of a cable into the port and the other end
          into a computer or other network device, the Link light should come on.
          If it doesn’t, something is wrong with the cable, the hub (or switch port),
          or the device on the other end of the cable.
        ✦ Each port may also have an LED indicator that flashes to indicate net-
          work activity. If you stare at a switch for awhile, you can find out who
          uses the network most by noting which activity indicators flash the most.
        ✦ The ports may also have a Collision indicator that flashes whenever a
          packet collision occurs on the port. It’s perfectly acceptable for this light
          to flash now and then, but if it flashes a lot, you may have a problem
          with the network. Usually this just means that the network is overloaded
          and should be segmented with a switch to improve performance. But in
          some cases, a flashing Collision indicator may be caused by a faulty net-
          work node that clogs up the network with bad packets.



Daisy-Chaining Switches
       If a single switch doesn’t have enough ports for your entire network,
       you can connect switches together by daisy-chaining them. If one of the
       switches has an uplink port, you can use a normal patch cable to connect
       the uplink port to one of the regular ports on the other switch. If neither
110   Daisy-Chaining Switches


         device has an uplink port, use a crossover cable to connect them. (For
         instructions on making a crossover cable, see the section, “Crossover
         cables,” earlier in this chapter.)

         On some hubs and switches, a button is used to switch one of the ports
         between a normal port and an uplink port. This button is often labeled MDI/
         MDIX. To use the port as a normal port, switch the button to the MDI posi-
         tion. To use the port as an uplink port, switch the button to MDIX.

         Some hubs and switches have a separate jack for the uplink port, but it turns
         out that the uplink port shares one of the normal ports internally. If that’s
         the case, plugging a cable into the uplink port disables one of the normal
         ports. You shouldn’t plug cables into both of these jacks. If you do, the
         switch won’t work properly.

         Note that the number of switches that you can chain together is limited. For
         10BaseT networks, you shouldn’t connect more than three switches to each
         other. For 100 Mbps or gigabit segments, you can chain only two switches
         together.

         You can get around this rule by using stackable switches. Stackable switches
         have a special type of cable connector that connects two or more switches
         in a way that lets them function as if they were a single switch. Stackable
         switches are a must for large networks.
       Chapter 3: Setting Up
       a Network Server
       In This Chapter
       ✓ Thinking about the different ways to install a network operating
         system
       ✓ Getting ready for the installation
       ✓ Installing a network operating system
       ✓ Figuring out what to do after you install the network operating system




       A     fter you’ve installed the network cables and other devices, such as
             hubs and switches, the next step in building a network is usually set-
       ting up a server. After you’ve physically connected the server computer
       to the network, you can install the network operating system (NOS) on the
       server. Then, you can configure it to provide the network services that you
       expect and need from the server.



The Many Ways to Install a
Network Operating System
       Regardless of which network operating system you choose to use for your
       network servers, you can use any of several common ways to actually install
       the NOS software on the server computer. The following sections describe
       these alternatives.


       Full install versus upgrade
       One of the basic NOS installation choices is whether you want to perform a
       full installation or an upgrade installation. In some cases, you may be better
       off performing a full installation even if you’re installing the NOS on a com-
       puter that already has an earlier version of the NOS installed.
112   The Many Ways to Install a Network Operating System


          ✦ If you’re installing the NOS on a brand-new server, you’ll be performing
            a full installation that installs the operating system and configures it with
            default settings.
          ✦ If you’re installing the NOS on a server computer that already has a
            server operating system installed, you can perform an upgrade installa-
            tion that replaces the existing operating system with the new one but
            retains as many of the settings from the existing operating system as
            possible.
          ✦ You can also perform a full installation on a computer that already has
            an operating system installed. In that case, you have the option of delet-
            ing the existing operating system or performing a multiboot installation
            that installs the new server operating system alongside the existing
            operating system. Then, when you restart the computer, you can choose
            which operating system you want to run.
          ✦ Although multiboot installation may sound like a good idea, it’s fraught
            with peril. I suggest that you avoid multiboot unless you have a specific
            reason to use it. For more information about multiboot setups, see the
            sidebar, “Giving multiboot the boot.”
          ✦ You can’t upgrade a client version of Windows to a server version.
            Instead, you must perform a full installation, which deletes the existing
            Windows operating system, or a multiboot installation, which leaves
            the existing client Windows intact. Either way, however, you can pre-
            serve existing data on the Windows computer when you install the
            server version.


         Installing over the network
         Normally, you install the NOS directly from the CD-ROM distribution discs
         on the server’s CD-ROM drive. However, you can also install the operating
         system from a shared drive located on another computer, provided that the
         server computer already has access to the network. You can either use a
         shared CD-ROM drive or you can copy the entire contents of the distribution
         CD-ROM disc onto a shared hard drive.

         Obviously, the server computer must have network access in order for this
         technique to work. If the server already has an operating system installed,
         it probably already has access to the network. If not, you can boot the com-
         puter from a floppy that has basic network support.

         If you’re going to install the NOS onto more than one server, you can save
         time by first copying the distribution CD onto a shared hard drive. That’s
         because even the fastest CD-ROM drives are slower than the network. Even
         with a basic 10 Mbps network, access to hard drive data over the network is
         much faster than access to a local CD-ROM drive.
                 The Many Ways to Install a Network Operating System                           113


                         Giving multiboot the boot
Multiboot installations enable you to have more    install each operating system into its own disk
than one operating system on a single com-         partition. Although most network operating
puter. Of course, only one of these operating      systems let you install two (or more) operat-
systems can be running at any time. When you       ing systems into a single partition, doing so is
boot the computer, a menu appears with each        not a very good idea. To support two operating
of the installed operating systems listed. You     systems in a single partition, the operating sys-
can choose which operating system to boot          tems have to play a risky shell game with key
from this menu.                                    system files — moving or renaming them each
                                                   time you restart the computer. Unfortunately,         Book II
Multiboot is most useful for software develop-                                                          Chapter 3
                                                   things can go wrong. For example, if lightning
ers or network managers who want to make
                                                   strikes and the power goes out just as the NOS
sure that software is compatible with a wide
                                                   is switching the startup files around, you may




                                                                                                           Network Server
variety of operating systems. Rather than set




                                                                                                            Setting Up a
                                                   find yourself with a server that can’t boot to any
up a bunch of separate computers with differ-
                                                   of its installed operating systems.
ent operating system versions, you can install
several operating systems on a single PC and       The best way to set up a multiboot system is to
use that one PC to test the software. For pro-     install each operating system into its own par-
duction network servers, however, you proba-       tition. Then, you can use a boot manager pro-
bly don’t need to have more than one operating     gram to choose the partition you want to boot
system installed.                                  from when you start the computer.
If you still insist on loading two or more oper-
ating systems on a network server, be sure to




          Automated and remote installations
          In case you find yourself in the unenviable position of installing a NOS onto
          several servers, you can use a few tricks to streamline the process:

           ✦ Automated setup lets you create a setup script that provides answers to
             all the questions asked by the installation program. After you’ve created
             the script, you can start the automated setup, leave, and come back
             when the installation is finished. Creating the setup script is a bit of
             work, so automated setup makes sense only if you have more than a few
             servers to install.
           ✦ Microsoft has a feature called Remote Installation Services (RIS) that lets
             you install Windows server versions from a remote network location
             without even going to the server computer. This is tricky to set up, how-
             ever, so it’s really worth it only if you have a lot of servers on which to
             install operating systems. (You can also use RIS to install client operat-
             ing systems.)
114   Gathering Your Stuff


Gathering Your Stuff
         Before you install a network operating system, you should gather every-
         thing you need so you don’t have to look for something in the middle of
         the setup. The following sections describe the items you’re most likely to
         need.


         A capable server computer
         Obviously, you have to have a server computer on which to install the NOS.
         Each NOS has a list of the minimum hardware requirements supported by
         the operating system. For example, Table 3-1 summarizes the minimum
         requirements for the Standard Edition of the current edition of Windows
         Server, known as Windows Server 2008 Rw.

         My suggestion is that you take these minimums with a grain of salt.
         Windows Server 2008 will crawl like a snail with 512MB of RAM; I wouldn’t
         bother with less than 4GB, and 16GB is a more appropriate minimum for
         most purposes.



           Table 3-1               Minimum Hardware Requirements
                                     for Windows Server 2008 R2
           Item                                  Windows Server 2008 R2
           CPU                                   1.4 GHz
           RAM                                   512MB
           Free disk space                       32GB


         You should also check your server hardware against the list of compatible
         hardware published by the maker of your NOS. For example, Microsoft
         publishes a list of hardware that it has tested and certified as compatible
         with Windows servers. This list is called the Hardware Compatibility List, or
         HCL for short. You can check the HCL for your specific server by going to
         Microsoft’s Web site at www.microsoft.com/whdc/hcl/default.mspx.
         You can also test your computer’s compatibility by running the Check
         System Compatibility option from the Windows distribution CD-ROM.

         You can find more specific details on server computer recommendations in
         Book I, Chapter 3.
                                            Gathering Your Stuff      115

The server operating system
You also need a server operating system to install. You’ll need either the
distribution CDs or DVDs or access to a copy of them over the network. In
addition to the discs, you should have the following:

 ✦ The product key: The installation program asks you to enter the prod-
   uct key during the installation to prove that you have a legal copy of the
   software. If you have the actual CDs or DVDs, the product key should be
   on a sticker attached to the case.
 ✦ Manuals: If the operating system came with printed manuals, you should
   keep them handy.                                                              Book II
 ✦ Your license type: You can purchase Microsoft operating systems on a         Chapter 3
   per-server or a per-user/per device basis. You need to know which plan
   you have when you install the NOS.




                                                                                   Network Server
                                                                                    Setting Up a
Check the CD or DVD distribution disc for product documentation and addi-
tional last-minute information. For example, Windows servers have a \docs
folder that contains several files that have useful setup information.


Other software
In most cases, the installation program should be able to automatically con-
figure your server’s hardware devices and install appropriate drivers. Just
in case, though, you should dig out the driver disks that came with your
devices, such as network interface cards, SCSI devices, DVD drives, printers,
scanners, and so on.


A working Internet connection
This isn’t an absolute requirement, but the installation will go much
smoother if you have a working Internet connection before you start. The
installation process may use this Internet connection for several things:

 ✦ Downloading late-breaking updates or fixes to the operating system.
   This can eliminate the need to install a service pack after you finish
   installing the NOS.
 ✦ Locating drivers for nonstandard devices. This can be a big plus if you
   can’t find the driver disk for your obscure SCSI card.
 ✦ Activating the product after you complete the installation (for
   Microsoft operating systems).
116   Making Informed Decisions


         A good book
         You’ll spend lots of time watching progress bars during installation, so you
         may as well have something to do while you wait. May I recommend The
         Hitchhiker’s Guide to the Galaxy?



Making Informed Decisions
         When you install a NOS, you have to make some decisions about how you
         want the operating system and its servers configured. Most of these decisions
         aren’t cast in stone, so don’t worry if you’re not 100 percent sure how you
         want everything configured. You can always go back and reconfigure things.
         However, you’ll save yourself time if you make the right decisions up front
         rather than just guess when the setup program starts asking you questions.

         The following list details most of the decisions that you’ll need to make.
         (This list is for Windows Server 2003 and 2008 installations. For other net-
         work operating systems, the decisions may vary slightly.)

          ✦ The existing operating system: If you want to retain the existing operating
            system, the installation program can perform a multiboot setup, which
            allows you to choose which operating system to boot to each time you
            start the computer. This is rarely a good idea for server computers, so I
            recommend that you elect to delete the existing operating system.
          ✦ Partition structure: Most of the time, you’ll want to treat the entire
            server disk as a single partition. However, if you want to divide the disk
            into two or more partitions, you should do so during setup. (Unlike most
            of the other setup decisions, this one is hard to change later.)
          ✦ File system: Windows servers provide two choices for the file system to
            format the server’s disk: FAT32 and NTFS. In every case, you should elect
            to use NTFS. FAT32 should never be used for a server operating system.
          ✦ Computer name: During the operating system setup, you’re asked to
            provide the computer name used to identify the server on the network.
            If your network has only a few servers, you can just pick a name such
            as Server01 or MyServer. If your network has more than a few servers,
            you’ll want to follow an established guideline for creating server names.
          ✦ Administrator password: Okay, this one is tough. You don’t want to pick
            something obvious, like Password, Administrator, or your last name.
            On the other hand, you don’t want to type in something random that
            you’ll later forget, because you’ll find yourself in a big pickle if you forget
            the administrator password. I suggest that you make up a complex
            password consisting of a mix of uppercase and lowercase letters, some
            numerals, and a special symbol or two; then write it down and keep it in
            a secure location where you know it won’t get lost.
                               Installing a Network Operating System          117

        ✦ Networking protocols: You’ll almost always need to install the TCP/
          IP protocol, the Microsoft network client protocol, and file and printer
          sharing. Depending on how the server will be used, you may want to
          install other protocols as well.
        ✦ TCP/IP configuration: You’ll need to know what IP address to use for
          the server. Even if your network has a DHCP server to dynamically
          assign IP addresses to clients, most servers use static IP addresses.
        ✦ Workgroup or domain: You’ll need to decide whether the server will
          join a domain or just be a member of a workgroup. In either case, you’ll
          need to know the domain name or the workgroup name.
                                                                                        Book II
                                                                                       Chapter 3
Final Preparations




                                                                                          Network Server
       Before you begin the actual installation, you should take a few more steps:




                                                                                           Setting Up a
        ✦ Clean up the server’s disk by uninstalling any software that you don’t
          need and removing any old data that is no longer needed. This cleanup
          is especially important if you’re converting a computer that’s been in
          use as a client computer to a server. You probably don’t need Microsoft
          Office or a bunch of games on the computer after it becomes a server.
        ✦ Do a complete backup of the computer. Operating system setup programs
          are almost flawless, so the chances of losing data during installation are
          minimal. But you still face the chance that something may go wrong.
        ✦ If the computer is connected to an uninterruptible power supply (UPS)
          that has a serial or USB connection to the computer, unplug the serial
          or USB connection. In some cases, this control connection can confuse
          the operating system’s setup program when it tries to determine which
          devices are attached to the computer.
        ✦ If the computer has hard drives compressed with DriveSpace or
          DoubleSpace, uncompress the drives before you begin.
        ✦ Light some votive candles, take two Tylenol, and put on a pot of coffee.



Installing a Network Operating System
       The following sections present an overview of a typical installation of
       Windows Server 2008. Although the details vary, the overall installation pro-
       cess for other network operating systems is similar.

       In most cases, the best way to install Windows Server 2008 is to perform
       a new install directly from the DVD installation media. Although upgrade
       installs are possible, your server will be more stable if you perform a new
       install. (For this reason, most network administrators avoid upgrading to
       Windows Server 2008 until it’s time to replace the server hardware.)
118   Installing a Network Operating System


         To begin the installation, insert the DVD distribution media in the server’s
         DVD drive and then restart the server. This causes the server to boot
         directly from the distribution media, which initiates the setup program.

         As the setup program proceeds, it leads you through two distinct installa-
         tion phases: Collecting Information and Installing Windows. The following
         sections describe these installation phases in greater detail.


         Phase 1: Collecting Information
         In the first installation phase, the setup program asks for the preliminary
         information that it needs to begin the installation. A setup wizard prompts
         you for the following information:

          ✦ Language: Select your language, time-zone, and keyboard type.
          ✦ Product Key: Enter the 25-character product key that came with the
            installation media. If setup says you entered an invalid product key,
            double-check it carefully. You probably just typed the key incorrectly.
          ✦ Operating System Type: The setup program lets you select Windows
            Server 2008 Standard Edition or Core. Choose Standard Edition to install
            the full server operating system; choose Core if you want to install the
            new text-only version.
          ✦ License Agreement: The official license agreement is displayed. You
            have to agree to its terms in order to proceed.
          ✦ Install Type: Choose an Upgrade or Clean Install type.
          ✦ Disk Location: Choose the partition in which you want to install
            Windows.
          ✦ Upgrade to NTFS: If you want to upgrade a FAT32 system to NTFS, you’ll
            need to say so now.


         Phase 2: Installing Windows
         In this phase, Windows setup begins the actual process of installing
         Windows. The following steps are performed in sequence:

          1. Copying Files: Compressed versions of the installation files are copied
             to the server computer.
          2. Expanding Files: The compressed installation files are expanded.
          3. Installing Features: Windows server features are installed.
          4. Installing Updates: The setup program checks Microsoft’s Web site and
             downloads any critical updates to the operating system.
          5. Completing Installation: When the updates are installed, the setup pro-
             gram reboots so it can complete the installation.
                                                       Configuring Your Server       119

Configuring Your Server
              After you’ve installed Windows Server 2008, the computer automatically
              reboots, and you’re presented with the Initial Configuration Tasks Wizard,
              as shown in Figure 3-1. This wizard guides you through the most important
              initial tasks for configuring your new server.




                                                                                               Book II
                                                                                              Chapter 3




                                                                                                 Network Server
                                                                                                  Setting Up a
Figure 3-1:
Initial
Configura-
tion Tasks.



              The following list describes the server configuration settings available from
              this wizard:

               ✦ Set the Administrator Password: The very first thing you should do
                 after installing Windows is set a secure administrator password.
               ✦ Set the Time Zone: This is necessary only if the indicated time zone is
                 incorrect.
               ✦ Configure Networking: The default network settings are usually appro-
                 priate, but you can use this option to change the defaults if you wish.
               ✦ Provide Computer Name and Domain: This option lets you change the
                 server’s computer name and join a domain.
               ✦ Enable Automatic Updating: Use this option if you want to let the server
                 automatically check for operating system updates.
               ✦ Download and Install Updates: Use this option to check for critical
                 operating system updates.
               ✦ Add Roles: This option launches the Add Roles Wizard, which lets you
                 configure important roles for your server.
120   Configuring Your Server


          ✦ Add Features: This option lets you add more operating system features.
          ✦ Enable Remote Desktop: Use this option to enable the Remote Desktop
            feature, which lets you administer this server from another computer.
          ✦ Configure Windows Firewall: If you want to use the built-in Windows
            firewall, this option lets you configure it.
       Chapter 4: Configuring
       Windows Clients
       In This Chapter
       ✓ Configuring network connections for Windows clients
       ✓ Setting the computer name, description, and workgroup
       ✓ Joining a domain
       ✓ Setting logon options




       B     efore your network setup is complete, you must configure the net-
             work’s client computers. In particular, you have to configure each
       client’s network interface card so that it works properly, and you have to
       install the right protocols so that the clients can communicate with other
       computers on the network.

       Fortunately, the task of configuring client computers for the network is
       child’s play in Windows. For starters, Windows automatically recognizes
       your network interface card when you start up your computer. All that
       remains is to make sure that Windows properly installed the network proto-
       cols and client software.

       With each version of Windows, Microsoft has simplified the process of con-
       figuring client network support. In this chapter, I describe the steps for con-
       figuring networking for Windows XP, Vista, and Windows 7.



Configuring Network Connections
       Windows automatically detects the presence of a network adapter; nor-
       mally, you don’t have to install device drivers manually for the adapter.
       When Windows detects a network adapter, it automatically creates a net-
       work connection and configures it to support basic networking protocols.
       However, you may need to change the configuration of a network connec-
       tion manually. The procedures for Windows XP and Vista are described in
       the following sections.
122     Configuring Network Connections


              Configuring Windows XP network connections
              The following steps show how to configure your network connection on a
              Windows XP system:

              1. Choose Start➪Control Panel to open the Control Panel.
                 The Control Panel appears.
              2. Double-click the Network Connections icon.
                 The Network Connections folder appears, as shown in Figure 4-1.




Figure 4-1:
The
Network
Connections
folder.



              3. Right-click the connection that you want to configure and then choose
                 Properties from the menu that appears.
                 Or you can select the network connection and click Change Settings of
                 This Connection in the task pane.
                 Either way, the Properties dialog box for the network connection
                 appears, as shown in Figure 4-2.
              4. To configure the network adapter card settings, click Configure.
                 This action summons the Properties dialog box for the network adapter,
                 as shown in Figure 4-3. This dialog box has five tabs that let you config-
                 ure the NIC:
                  • General: This tab shows basic information about the NIC, such as
                    the device type and status. For example, the device shown in Figure
                    4-3 is an Intel Pro 100 network interface. (It’s installed in slot 3 of the
                    computer’s PCI bus.)
                                       Configuring Network Connections          123




Figure 4-2:
The
Properties
dialog                                                                                    Book II
box for a                                                                                Chapter 4
network
connection.




                                                                                            Windows Clients
                                                                                              Configuring
                If you’re having trouble with the adapter, you can click the Trouble-
                shoot button to open the Windows XP Hardware Troubleshooter.
                You can also disable the device if it’s preventing other components
                of the computer from working properly.
              • Advanced: This tab lets you set a variety of device-specific param-
                eters that affect the operation of the NIC. For example, some cards
                allow you to set the speed parameter (typically at 10 Mbps or 100
                Mbps) or the number of buffers the card should use.
                Consult the manual that came with the card before you play around
                with any of those settings.
              • Driver: This tab displays information about the device driver that’s
                bound to the NIC and lets you update the driver to a newer version,
                roll back the driver to a previously working version, or uninstall the
                driver.
              • Resources: With this tab, you can use manual settings to limit the
                system resources used by the card — including the memory range,
                I/O range, IRQ, and DMA channels.
                In the old days, before Plug and Play cards, you had to configure
                these settings whenever you installed a card, and it was easy to
                create resource conflicts. Windows configures these settings auto-
                matically so that you should rarely need to fiddle with them.
              • Power Management: This tab lets you set power-management
                options. You can specify that the network card be shut down when-
                ever the computer goes into sleep mode — and that the computer
                wake up periodically to refresh its network state.
124      Configuring Network Connections




Figure 4-3:
The
Properties
dialog
box for a
network
adapter.



                 When you click OK to dismiss the network adapter’s Properties dialog box,
                 the network connection’s Properties dialog box closes. Select the Change
                 Settings of This Connection option again to continue the procedure.
              5. Make sure that the network items your client requires are listed in the
                 network connection Properties dialog box.
                 The following list describes the items you commonly see listed here.
                 Note that not all networks need all these items:
                  • Client for Microsoft Networks: This item is required if you want to
                    access a Microsoft Windows network. It should always be present.
                  • File and Printer Sharing for Microsoft Networks: This item allows your
                    computer to share its files or printers with other computers on the
                    network.
                    This option is usually used with peer-to-peer networks, but you can
                    use it even if your network has dedicated servers. However, if you
                    don’t plan to share files or printers on the client computer, you
                    should disable this item.
                  • Internet Protocol (TCP/IP): This item enables the client computer to
                    communicate by using the TCP/IP protocol.
                    If all servers on the network support TCP/IP, this protocol should be
                    the only one installed on the client.
                  • NWLink IPX/SPX/NetBIOS Compatible Transport Protocol: This pro-
                    tocol is required only if your network needs to connect to an older
                    NetWare network that uses the IPX/SPX protocol.
                    In most modern networks, you should enable TCP/IP only and leave
                    this item disabled.
                               Configuring Network Connections           125

 6. If a protocol that you need isn’t listed, click the Install button to add
    the needed protocol.
    A dialog box appears, asking whether you want to add a network client,
    protocol, or service. Click Protocol and then click Add. A list of available
    protocols appears. Select the one you want to add; then click OK. (You
    may be asked to insert a disc or the Windows CD.)
 7. Make sure that the network client that you want to use appears in the
    list of network resources.
    For a Windows-based network, make sure that Client for Microsoft
    Networks is listed. For a NetWare network, make sure that Client Service
    for NetWare appears. If your network uses both types of servers, you            Book II
    can choose both clients.                                                       Chapter 4

    If you have NetWare servers, use the NetWare client software that comes




                                                                                      Windows Clients
    with NetWare rather than the client supplied by Microsoft with Windows.




                                                                                        Configuring
 8. If the client that you need isn’t listed, click the Install button to add
    the client that you need, click Client, and then click Add. Then choose
    the client that you want to add and click OK.
    The client you select is added to the network connection’s Properties
    dialog box.
 9. To remove a network item that you don’t need (such as File and
    Printer Sharing for Microsoft Networks), select the item and click the
    Uninstall button.
    For security reasons, you should make it a point to remove any clients,
    protocols, or services that you don’t need.
10. To configure TCP/IP settings, click Internet Protocol (TCP/IP) and
    click Properties to display the TCP/IP Properties dialog box. Adjust
    the settings and then click OK.
    The TCP/IP Properties dialog box, shown in Figure 4-4, lets you choose
    from these options:
     • Obtain an IP Address Automatically: Choose this option if your net-
       work has a DHCP server that assigns IP addresses automatically.
       Choosing this option drastically simplifies the administering of TCP/
       IP on your network. (See Book IV, Chapter 3, for more information
       about DHCP.)
     • Use the Following IP Address: If your computer must have a specific
       IP address, choose this option and then type the computer’s IP
       address, subnet mask, and default gateway address. (For more infor-
       mation about these settings, see Book IV, Chapter 2.)
     • Obtain DNS Server Address Automatically: The DHCP server can also
       provide the address of the Domain Name System (DNS) server that the
       computer should use. Choose this option if your network has a DHCP
       server. (See Book IV, Chapter 4, for more information about DNS.)
126     Configuring Network Connections


                   • Use the Following DNS Server Addresses: Choose this option if a DNS
                     server isn’t available. Then type the IP address of the primary and
                     secondary DNS servers.




Figure 4-4:
Configuring
TCP/IP.




              Configuring Windows Vista network connections
              The procedure for configuring a network connection on Windows Vista is
              similar to the procedure for Windows XP, except that Microsoft decided to
              bury the configuration dialog boxes a little deeper in the bowels of Windows.

              To find the settings you need, follow these steps:

              1. Choose Start➪Control Panel to open the Control Panel.
                  The Control Panel appears.
              2. Choose View Network Status and Tasks under the Network and
                  Internet heading.
                  This step opens the Network and Sharing Center, shown in Figure 4-5.
              3. Click Manage Network Connections.
                  The Network Connections folder appears, as shown in Figure 4-6.
              4. Right-click the connection that you want to configure and then choose
                  Properties from the menu that appears.
                                           Configuring Network Connections          127




Figure 4-5:
The
                                                                                               Book II
Network
                                                                                              Chapter 4
and Sharing
Center




                                                                                                 Windows Clients
(Windows




                                                                                                   Configuring
Vista).




Figure 4-6:
The
Network
Connections
folder
(Windows
Vista).



                 The Properties dialog box for the network connection appears, as shown
                 in Figure 4-7. If you compare this dialog box with the dialog box that was
                 shown earlier, in Figure 4-2, you see that they’re the same.
              5. Click Configure to configure the network connection.
128      Configuring Network Connections


                  From this point, the steps for configuring the network connection are
                  the same as they are for Windows XP. As a result, you can continue,
                  beginning with Step 4 in the previous section, “Configuring Windows XP
                  network connections.”




Figure 4-7:
The
Properties
dialog
box for a
network
connection
(Windows
Vista).




              Configuring Windows 7 network connections
              The procedure to configure a Windows 7 network connection is similar to the
              Windows Vista procedure, with just a few minor variations. Here are the steps:

              1. Choose Start➪Control Panel to open the Control Panel.
                  The Control Panel appears.
              2. Choose View Network Status and Tasks under the Network and
                  Internet heading.
                  This step opens the Network and Sharing Center, shown in Figure 4-8.
              3. Click the Change Adapter Settings link on the left.
                  The Network Connections folder appears, as shown in Figure 4-9.
              4. Right-click the connection that you want to configure and then choose
                  Properties from the menu that appears.
                  The Properties dialog box for the network connection appears, as shown
                  in Figure 4-10. If you compare this dialog box with the dialog box that
                  was shown earlier, in Figure 4-2, you see that they’re the same.
               Configuring Network Connections   129




                                                        Book II
                                                       Chapter 4

Figure 4-8:




                                                          Windows Clients
The




                                                            Configuring
Network
and Sharing
Center
(Windows 7).




Figure 4-9:
The
Network
Connections
folder
(Windows 7).
130     Configuring Client Computer Identification


               5. Click Configure to configure the network connection.
                   From this point, the steps for configuring the network connection are
                   the same as they are for Windows XP. As a result, you can continue,
                   beginning with Step 4 in the earlier section, “Configuring Windows XP
                   network connections.”




Figure 4-10:
The
Properties
dialog
box for a
network
connection
(Windows 7).




Configuring Client Computer Identification
               Every client computer must identify itself to participate in the network.
               The computer identification consists of the computer’s name, an optional
               description, and the name of either the workgroup or the domain to which
               the computer belongs.

               The computer name must follow the rules for NetBIOS names; it may be 1 to 15
               characters long and may contain letters, numbers, or hyphens but no spaces
               or periods. For small networks, it’s common to make the computer name
               the same as the username. For larger networks, you may want to develop a
               naming scheme that identifies the computer’s location. For example, a name
               such as C-305-1 may be assigned to the first computer in Room 305 of
               Building C. Or MKTG010 may be a computer in the Marketing department.

               If the computer will join a domain, you need to have access to an
               Administrator account on the domain, unless the administrator has already
               created a computer account on the domain. Note that only the following ver-
               sions of Windows have the ability to join a domain:
                                  Configuring Client Computer Identification       131

                ✦ Windows 7 Professional, Enterprise, or Ultimate
                ✦ Windows Vista Business, Enterprise, or Ultimate
                ✦ Windows XP Professional

               When you install Windows on the client system, the Setup program asks for
               the computer name and workstation or domain information. You can change
               this information later, if you want. The procedure varies depending on the
               Windows version you’re using.


               Configuring Windows XP computer identification                                Book II
               To change the computer identification in Windows XP, follow these steps:
                                                                                            Chapter 4

               1. Open the Control Panel and double-click the System icon to open the




                                                                                               Windows Clients
                   System Properties dialog box.




                                                                                                 Configuring
               2. Click the Computer Name tab.
                   The computer identification information is displayed.
               3. Click the Change button.
                   This step displays the Computer Name Changes dialog box, as shown in
                   Figure 4-11.
               4. Type the new computer name and then specify the workgroup or
                   domain information.
                   To join a domain, select the Domain radio button and type the domain
                   name into the appropriate text box. To join a workgroup, select the
                   Workgroup radio button and type the workgroup name in the corre-
                   sponding text box.
               5. Click OK.




Figure 4-11:
The
Computer
Name
Changes
dialog box
(Windows
XP).
132     Configuring Client Computer Identification


               6. If you’re prompted, enter the username and password for an
                  Administrator account.
                  You’re asked to provide this information only if a computer account has
                  not already been created for the client computer.
               7. When a dialog box appears, informing you that you need to restart the
                  computer, click OK. Then restart the computer.
                  You’re done!


               Configuring Windows Vista or Windows 7
               computer identification
               To change the computer identification in Windows Vista or Windows 7,
               follow these steps:

               1. Click the Start button, and then right-click Computer and choose
                  Properties.
                  This step displays the System information window, as shown in Figure
                  4-12. Notice the section that lists computer name, domain, and work-
                  group settings.
               2. Click the Change Settings link in the lower-right.




Figure 4-12:
The System
information
window
(Windows 7).
                                 Configuring Client Computer Identification         133

                  If a dialog box appears and asks for your permission to continue, click
                  Continue. The System Properties dialog box then appears, as shown in
                  Figure 4-13.
               3. Click the Change button.
                  This step displays the Computer Name/Domain Changes dialog box, as
                  shown in Figure 4-14.
               4. Enter the computer name and the workgroup or domain name.
                  If you want to join a domain, choose the Domain option button and type
                  the domain name. To join a workgroup, choose the Workgroup option
                  button and type the workgroup name.
                                                                                             Book II
                                                                                            Chapter 4




                                                                                               Windows Clients
                                                                                                 Configuring
Figure 4-13:
The System
Properties
dialog box
(Windows 7).




Figure 4-14:
The
Computer
Name/
Domain
Changes
dialog box
(Windows 7).
134   Configuring Network Logon


         5. Click OK.
         6. Enter the username and password for an Administrator account when
             prompted.
             You’re asked to provide this information only if a computer account
             hasn’t already been created for the client computer.
         7. When a dialog box appears, informing you that you need to restart the
             computer, click OK. Then restart the computer.
             The computer is then added to the domain or workgroup.



Configuring Network Logon
         Every user who wants to access a domain-based network must log on to the
         domain by using a valid user account. The user account is created on the
         domain controller — not on the client computer.

         Network logon isn’t required to access workgroup resources. Instead, work-
         group resources can be password-protected to restrict access.

         When you start a Windows computer that’s been configured to join
         a domain, as described in the section “Configuring Client Computer
         Identification,” earlier in this chapter, the Log On to Windows dialog box is
         displayed. The user can use this dialog box to log on to a domain by entering
         a domain username and password and then selecting the domain that she
         wants to log on to (from the Log On To drop-down list).

         You can create local user accounts in Windows that allow users to access
         resources on the local computer. To log on to the local computer, the user
         selects This Computer from the Log On To drop-down list and enters the
         username and password for a local user account. When a user logs on by
         using a local account, he isn’t connected to a network domain. To log on to a
         domain, the user must select the domain from the Log On To drop-down list.

         If the computer isn’t part of a domain, Windows can display a friendly logon
         screen that displays an icon for each of the computer’s local users. The user
         can log on simply by clicking the appropriate icon and entering a password.
         (This feature isn’t available for computers that have joined a domain.)

         Note that if the user logs on by using a local computer account rather than a
         domain account, she can still access domain resources. A Connect To dialog
         box appears whenever the user attempts to access a domain resource. Then
         the user can enter a domain username and password to connect to the
         domain.
      Chapter 5: Macintosh Networking
      In This Chapter
      ✓ Hooking up a Macintosh network
      ✓ Using a Macintosh network
      ✓ Mixing Macs and PCs




      T   his book dwells on networking Windows-based computers, as if
          Microsoft were the only game in town. (Hah! They wish.) To be politi-
      cally correct, I should at least acknowledge the existence of a different
      breed of computer: the Apple Macintosh.

      This chapter presents what you need to know to hook up a Macintosh
      network, use a Macintosh network, and mix Macintoshes and Windows
      PCs on the same network. This chapter isn’t a comprehensive tome on
      Macintoshes, but it’s enough to start.



What You Need to Know to Hook
Up a Macintosh Network
      The following sections present some key things you should know about net-
      working Macintosh computers before you start plugging in cables.


      Mac networking protocols
      Every Macintosh ever built, even an original 1984 model, includes network-
      ing support. Of course, newer Macintosh computers have better built-in
      networking features than older Macintosh computers. The newest Macs
      include built-in gigabit Ethernet adapters and sophisticated networking sup-
      port built in to the operating system — similar to the networking features
      that come with Windows. Because the network support is built in, you don’t
      have to fuss with installing and configuring the network.

      Originally, Macintosh computers used a set of networking protocols collec-
      tively known as AppleTalk. In the mid 1990s, AppleTalk was supplanted by a
      networking scheme called Open Transport.
136     What You Need to Know to Hook Up a Macintosh Network




                   Who’s winning in the AFP West?
  AFP is not a division of the NFL but an abbrevia-   NetWare and all versions of Windows since
  tion for AppleTalk Filing Protocol. It’s the part   Windows 95 use AFP to support Macintoshes
  of AppleTalk that governs how files are stored      in their networks.
  and accessed on the network. AFP allows files
                                                      In case you’re interested (and you shouldn’t
  to be shared with non-Macintosh computers.
                                                      be), AFP is a Presentation layer protocol. (See
  You can integrate Macintoshes into any net-
                                                      Book I, Chapter 2, if you don’t have a clue about
  work operating system that recognizes AFP.
                                                      what I’m talking about.)



            The current generation of Macintosh computers uses industry-standard
            TCP/IP networking. The only protocol left over from the AppleTalk days that
            is still in widespread use is AFP, used to enable file sharing. For a brief expla-
            nation of this protocol, see the sidebar “Who’s winning in the AFP West?”


            Mac OS X Server
            Apple offers a dedicated network operating system known as Mac OS
            X Server (the X is pronounced “Ten,” not “Ex”), which is designed for
            PowerMac G3 or later computers. Mac OS X Server is based on a Unix
            operating-system kernel known as Mach. Mac OS X Server can handle many
            network-server tasks as efficiently as any other network operating system,
            including Windows 2000, NetWare, and Unix.

            Mac OS X Server is the server version of the Mac OS X operating system,
            which is the current operating system version for client Macintosh computers.

            The Mac OS X Server includes the following features:

              ✦ Apache Web server, which also runs on Windows and Linux systems
              ✦ NetBoot, a feature that simplifies the task of managing network client
                computers
              ✦ File services using AFP
              ✦ WebObjects, a high-end tool for creating Web sites
              ✦ QuickTime Streaming Server, which lets the server broadcast multime-
                dia programs over the network
              What You Need to Know to Use a Macintosh Network                137

What You Need to Know to Use a Macintosh Network
      The following questions often come up after you install the network cable.
      Note that the following sections assume that you’re working with AppleTalk
      networking using Mac OS X. The procedures may vary somewhat if you’re
      using Open Transport networking or an earlier version of the Macintosh
      operating system.


      Configuring a Mac for networking
      Before you can access the network from your Mac, you must configure your
      Mac for networking: Activate AppleTalk and assign your network name and           Book II
      password.                                                                        Chapter 5


      Activating AppleTalk




                                                                                          Networking
                                                                                          Macintosh
      After all the cables are in place, you have to activate AppleTalk. Here’s how:

       1. Select the Chooser from the Apple menu.
          The Chooser is an application for choosing network resources.
       2. Click the Active button.
       3. Close the Chooser.

      Assigning your name and password
      After you activate AppleTalk, you’re ready to assign an owner name, a pass-
      word, and a name for your computer. This process allows other network
      users to access your Mac. Here’s how:

       1. Choose the File Sharing control panel from the Apple menu (Apple➪
          Control Panels➪File Sharing).
       2. Type your name in the Owner Name field.
       3. Type a password in the Owner Password field.
          Don’t forget what the password is.
       4. Type a descriptive name for your computer in the Computer Name
          field.
          Other network users will know your computer by this name.
       5. Click the Close button.
138   What You Need to Know to Use a Macintosh Network


         Accessing a network printer
         Accessing a network printer with AppleTalk is no different than accessing a
         printer when you don’t have a network. If more than one printer is available
         on the network, you use the Chooser to select the printer you want to use.
         Chooser displays all the available network printers — just pick the one you
         want to use. And keep the following points in mind:

          ✦ Be sure to enable Background Printing for the network printer. If you
            don’t, your Mac is tied up until the printer finishes your job — that can
            be a long time if someone else sent a 500-page report to the printer just
            before you. When you enable Background Printing, your printer output
            is captured to a disk file and then sent to the printer later while you con-
            tinue with other work.
             To enable Background Printing
             1. Choose Apple➪Chooser desk accessory.
             2. Select the printer you want to use from the Chooser.
             3. Click the Background Printing On button.
          ✦ Don’t enable Background Printing if a dedicated print server has
            been set up. In that case, print data is spooled automatically to the print
            server’s disk so your Mac doesn’t have to wait for the printer to become
            available.


         Sharing files with other users
         To share files on your Mac with other network users, you set up a shared
         resource. You can share a disk or just individual folders and restrict access
         to certain users.

         Before you can share files with other users, you must activate the AppleTalk
         file-sharing feature. Here’s how:

         1. Choose the File Sharing control panel from the Apple Menu.
         2. Click the Start button in the File Sharing section of the control panel.
         3. Click the Close button.

         To share a file or folder, click the file or folder once. Then open the File
         menu, choose Get Info, and choose Sharing from the submenu that appears.
         You can also use the Sharing section of the Info window to restrict access to
         the file or folder.
        What You Need to Know to Network Macintoshes with PCs                 139

      Accessing shared files
      To access files on another Macintosh, follow this procedure:

       1. Choose the Chooser from the Apple menu.
       2. Click the AppleShare icon from the Chooser window.
       3. Click the name of the computer you want to access. (If your network
          has zones, you must first click the zone you want to access.)
       4. Click OK.
          A logon screen appears.
                                                                                       Book II
       5. If you have a user account on the computer, click the Registered User       Chapter 5
          button and enter your username and password. Otherwise, click the
          Guest button and then click OK.




                                                                                         Networking
          A list of shared folders and disks appears.




                                                                                         Macintosh
       6. Click the folders and disks you want to access.
          A check box appears next to each item. If you check this box, you con-
          nect to the corresponding folder or disk automatically when you start
          your computer.
       7. Click OK.
      With Mac OS 8.5 and later, you can also use the Network Browser, found in
      the Apple menu, to access network drives or folders. Just open the Network
      Browser from the Apple menu, double-click the server that contains the shared
      disk or folder, and then double-click the drive or folder you want to use.



What You Need to Know to Network
Macintoshes with PCs
      Life would be too boring if Macs really lived on one side of the tracks and
      PCs lived on the other. If your organization has a mix of both Macs and
      PCs, odds are good that you eventually want to network them together.
      Fortunately, you have several ways:

       ✦ If your network has an OS X Server, you can use the Windows client soft-
         ware that comes with OS X Server to connect any version of Windows to
         the server. Doing so enables Windows users to access the files and print-
         ers on the Macintosh server.
140   What You Need to Know to Network Macintoshes with PCs


          ✦ The server versions of Windows include a feature called Services for
            Macintosh that allows Macintosh computers to access files and printers
            managed by the Windows servers without installing special client soft-
            ware on the Macintosh computers.
          ✦ If you use NetWare, you must purchase separate NetWare client software
            for your Macintosh computers. After you install this client software, the
            Macs can access files and printers managed by your NetWare servers.

         The biggest complication that occurs when you mix Macintosh and Windows
         computers on the same network is that the Mac OS and Windows have
         slightly different rules for naming files. For example:

          ✦ Macintosh filenames are limited to 31 characters, but Windows file-
            names can be up to 255 characters.
          ✦ Although a Macintosh filename can include any characters other than
            a colon, Windows filenames can’t include backslashes, greater-than or
            less-than signs, and a few other oddball characters.

         The best way to avoid filename problems is to stick with short names (under
         31 characters) and limit your filenames to letters, numbers, and common
         symbols (such as the hyphen or pound sign). Although you can translate any
         filenames that violate the rules of the system being used into a form that’s
         acceptable to both Windows and the Macintosh, doing so sometimes leads
         to cryptic or ambiguous filenames. But hey, network administration is as
         much an art as a science.
       Chapter 6: Configuring Other
       Network Features
       In This Chapter
       ✓ Setting up network printers
       ✓ Configuring your client computer’s Internet connections
       ✓ Mapping network drives




       A     fter you have your network servers and clients up and running, you
             still have many details to attend to before you can pronounce your
       network “finished.” In this chapter, you discover a few more configuration
       chores that have to be done: configuring Internet access, setting up network
       printers, configuring e-mail, and configuring mapped network drives.



Configuring Network Printers
       Before network users can print on the network, the network’s printers must
       be properly configured. For the most part, this is a simple task. All you have
       to do is configure each client that needs access to the printer.

       Before you configure a network printer to work with network clients, read
       the client configuration section of the manual that came with the printer.
       Many printers come with special software that provides more advanced
       printing and networking features than the standard features provided by
       Windows. If so, you may want to install the printer manufacturer’s software
       on your client computers rather than use the standard Windows network
       printer support.


       Adding a network printer
       The exact procedure for adding a network printer varies a bit, depending on
       the Windows version that the client runs. The following steps describe the
       procedure for Windows 7 (the procedure for Windows Vista is similar):

       1. Choose Start➪Devices and Printers.
       2. Click the Add a Printer button on the toolbar.
           This step starts the Add Printer Wizard, shown in Figure 6-1.
142      Configuring Network Printers




Figure 6-1:
The Add
Printer
Wizard
comes to
life.



                3. Select the Add a Network, Wireless or Bluetooth Printer option.
                   The wizard searches the network for available printers and displays a
                   list of the printers it finds, as shown in Figure 6-2.
                4. Click the printer you want to use.
                   If you can’t find the printer you want to use, click The Printer That I
                   Want Isn’t Listed and enter the UNC or IP address for the printer when
                   prompted.
                5. Click Next to add the printer.




Figure 6-2:
The Add
Printer
Wizard asks
you to pick a
printer.
                                                 Configuring Network Printers       143

                  The wizard copies to your computer the correct printer driver for the
                  network printer. (You may be prompted to confirm that you want to add
                  the driver. If so, click Install Driver to proceed.)
                  The Add Printer Wizard displays a screen that shows the printer’s name
                  and asks whether you want to designate the printer as your default
                  printer.
              6. If you want, designate the printer as your default printer.
              7. Click Next to continue.
                  A final confirmation dialog box is displayed.
              8. Click Finish.                                                               Book II
                                                                                            Chapter 6
                  You’re done!




                                                                                               Network Features
                                                                                               Configuring Other
              Accessing a network printer using a Web interface
              Printers that have a direct network connection often include a built-in Web
              server that lets you manage the printer from any browser on the network.
              For example, Figure 6-3 shows the home page for a Xerox Phaser 6125
              printer. This Web interface lets you view status information about the
              printer and check the printer’s configuration. You can even view error logs
              to find out how often the printer jams.




Figure 6-3:
Using a
printer’s
Web
interface.
144      Configuring Network Printers


               To call up a printer’s Web interface, enter its IP address or host name in the
               address bar of any Web browser.

               In addition to simply displaying information about the printer, you can also
               adjust the printer’s configuration from a Web browser. For example, Figure
               6-4 shows the Network Settings page for the Xerox printer. Here, you can
               change the network configuration details, such as the TCP/IP host name, IP
               address, subnet mask, domain name, and so on. Other configuration pages
               allow you to tell the printer to send an e-mail notification to an address that
               you specify whenever you encounter a problem with the printer.

               As the network administrator, you may need to visit the printer’s Web page
               frequently. I suggest that you add it to your browser’s Favorites menu so
               that you can get to it easily. If you have several printers, add them under a
               folder named Network Printers.




Figure 6-4:
Changing
network
settings via
a printer’s
Web
interface.
                                           Configuring Internet Access        145

Configuring Internet Access
       To enable the network users to access the Internet, you need to make sure
       that the TCP/IP configuration settings on each client computer are set cor-
       rectly. If you have a high-speed Internet connection, such as T1, DSL, cable,
       or ISDN, connected to the Internet via a router and your network uses DHCP
       for automatic TCP/IP configuration, you may not need to do anything special
       to get your clients connected to the Internet.


       Configuring clients for DHCP
       The easiest way to configure client computers to access the Internet via a        Book II
       shared high-speed connection is to use DHCP. DHCP automatically distrib-         Chapter 6
       utes the detailed TCP/IP configuration information to each client. Then, if
       your configuration changes, all you have to do is change the DHCP server’s




                                                                                           Network Features
                                                                                           Configuring Other
       configuration. You don’t have to manually change each client. Plus, the
       DHCP server avoids common manual configuration errors, such as assigning
       the same IP address to two computers.

       Before you configure the clients to use DHCP, you should first set up the
       DHCP server. The DHCP server’s configuration should include:

        ✦ A scope that specifies the range of IP addresses and the subnet mask to
          be distributed to client computers.
        ✦ The IP address of the router that should be used as the default gateway
          for client computers to reach the Internet.
        ✦ The IP addresses of the DNS servers that clients should use.

       Note that DHCP can be provided either by a server computer or by an intel-
       ligent router that has built-in DHCP. For more information about configuring
       DHCP, see Book IV, Chapter 3.

       After the DHCP server is configured, setting up Windows clients to use it is a
       snap. Just follow these steps for Windows 7:

       1. Open the Control Panel and click View Network Status and Tasks.
       2. Click Change Adapter Settings.
       3. Right-click the LAN connection icon and choose Properties.
           This brings up the Local Area Connection Properties dialog box, as
           shown in Figure 6-5.
146      Configuring Internet Access




Figure 6-5:
The Local
Area
Connection
Properties
dialog box.



               4. Select Internet Protocol Version 4 (TCP/IPv4) from the list of items
                  used by the connection and then click the Properties button.
                  This displays the Internet Protocol Version 4 (TCP/IP) Properties dialog
                  box, as shown in Figure 6-6.
               5. Make sure that both the Obtain An IP Address Automatically and
                  Obtain DNS Server Address Automatically options are selected.
                  These options enable DHCP for the client.




Figure 6-6:
The Internet
Protocol
Version 4
(TCP/IPv4)
Properties
dialog box.
                                               Mapping Network Drives           147

       6. Click OK to return to the Local Area Connection Properties dialog box
          and then click OK again.

      That’s all there is to it. The computer is now configured to use DHCP. You
      should check to make sure that every computer on your network is config-
      ured for DHCP.

      If your network doesn’t have a DHCP server, you’ll have to configure the
      TCP/IP configuration manually for each computer. Start by deciding the IP
      address that you want to assign to each computer. Then, follow the preced-
      ing procedure on every computer. When you get to Step 4, enter the comput-
      er’s IP address as well as the IP address of the default gateway (your Internet      Book II
      router) and the IP addresses of your DNS servers.                                   Chapter 6

      Frankly, setting up a DHCP server is a lot easier than manually configuring




                                                                                             Network Features
                                                                                             Configuring Other
      each computer’s TCP/IP information, unless your network has only two or
      three computers. So unless your network is tiny, get a DHCP server.


      Using Internet Connection Sharing
      Actually, the title of this section is misleading. It should be “Not Using
      Internet Connection Sharing.” Windows XP, Vista, and Windows 7 come with
      a built-in feature, called Internet Connection Sharing (ICS), designed to let you
      share an Internet connection with several computers on a small network.
      However, this feature is designed to be used only on very small networks
      that don’t have a separate router to enable the connection to be shared.

      All versions of Windows that support ICS also include a feature called the
      Windows Firewall that provides basic firewall support for home networks.
      This feature keeps hackers from invading your home network.

      I recommend that you use ICS and the Windows Firewall only for home net-
      works with no more than three computers. Even then, you’re better off pur-
      chasing an inexpensive connection-sharing device.

      If the Windows Firewall has been enabled and you don’t need it, you should
      disable it. Otherwise, it will disrupt your network. For information about
      how to enable or disable this feature, refer to Book III, Chapter 4.



Mapping Network Drives
      One of the main reasons that users want to use a network is to access
      shared disk storage located on network file servers. Although you can do
      this in several ways, the most common method is called mapping. Mapping
      assigns a drive letter to a shared folder on a network server. Then, the user
      can use the drive letter to access the shared folder as if it were a local drive.
148      Mapping Network Drives


              Before you map network drives for your network’s client computers, you
              should devise a strategy for how you’ll share folders and map them to
              drives. Here are just two possibilities:

               ✦ For private storage, you can create a separate shared folder for each
                 user on the file server and then map a drive letter on each user’s com-
                 puter to that user’s shared folder. For example, you can create shares
                 named jBrannan, dHodgson, and mCaldwell. Then, you can map drive
                 N: to jBrannan on jBrannan’s computer, dHodgson on dHodgson’s com-
                 puter, and mCaldwell on mCaldwell’s computer.
               ✦ For shared storage for an entire department, you can create a share for
                 the entire department and then map a drive to that share on each com-
                 puter in the department. For example, you may map drive M: to a share
                 named Marketing for the entire Marketing department to use.

              After you’ve decided how to map the file server’s shared folder, the next
              step is to create and share the folders on the server. For information about
              how to do that, refer to the appropriate chapters on specific network operat-
              ing systems later in this book.

              When you’re ready to map drives on the client computers, follow these
              steps:

              1. Choose Start➪Computer.
              2. Click the Map Network Drive button.
                  The Map Network Drive dialog box appears, as shown in Figure 6-7.




Figure 6-7:
Mapping
a network
drive.
                                        Mapping Network Drives         149

3. Select the drive letter that you want to map in the Drive drop-down list.
4. Type a valid path to the server and share that you want to map in the
    Folder text box.
    For example, to map a folder named pCaldwell on a server named
    MKTSERVER, type \\MKTSERVER\pCaldwell.
    If you don’t know the server or share name, click the Browse button and
    browse your way to the folder that you want to map.
5. To cause the network drive to be automatically mapped each time the
    user logs on, select the Reconnect at Logon check box.
    If you leave this check box deselected, the drive is mapped only until the    Book II
    next time you shut down Windows or log off.                                  Chapter 6

6. Click Finish.




                                                                                    Network Features
                                                                                    Configuring Other
    That’s it! You’re done.

If you’re the type who prefers to do things through the command line, you
can quickly map network drives by using the NET USE command at a com-
mand prompt. For example, here’s a NET USE command that maps drive Z:
to \\MKTSERVER\pCaldwell:

net use z: \\MKTSERVER\pCaldwell /persistent:yes

Specifying /persistent:yes causes the drive to be remapped each time
the user logs on. To remove a drive mapping via the command line, use a
command like this:

net use z: /delete

Here, the mapping for drive Z: is removed.

Manually setting up drive mappings as described here works well enough
for small networks but not so well for large networks. If a server or share
name changes, would you want to go to 200 computers in order to update
drive mappings? How about 2,000 computers? For larger networks, you’re
more likely to use either login scripts or group policies to configure network
storage for end users. You can find more information about login scripts and
group policies in Book VII, Chapters 4 and 6.
150   Book II: Building a Network
       Chapter 7: Verifying Your
       Network Installation
       In This Chapter
       ✓ Checking the network configuration settings
       ✓ Pinging yourself and others
       ✓ Making sure that you can log on
       ✓ Verifying mapped drives and checking network printers




       Y    ou’ve installed all the network cards, plugged in all the cables, and
            configured all the software. However, one task remains before you can
       declare your network finished: You must verify that the network works as
       expected.

       Verifying a network isn’t difficult. All you have to do is make sure that
       users can log on and access the network resources they need. If every-
       thing works the way it should, you can declare victory, give yourself a high
       five, and take the afternoon off. If not, you have to do some troubleshoot-
       ing to determine the source of the problem.

       In this short chapter, I describe some of the tests that you should perform to
       make sure that your network is functioning. Along the way, I suggest a few of
       the most common problems that may interrupt the network. However, the
       focus of this chapter is on verifying that your network is functioning — not on
       troubleshooting it if it isn’t. For information about network troubleshooting,
       refer to Book III, Chapters 6 and 7, as well as Book VII, Chapter 7.

       Incidentally, most of the techniques described in this chapter work from an
       MS-DOS command prompt. You can open a command prompt in Windows
       Vista or Windows 7 by clicking the Start button, typing cmd, and pressing
       Enter. In Windows XP, choose Start➪Run, type cmd, and then click OK.



Is the Computer Connected to the Network?
       This one is easy to check. Just check the Link light on the computer’s net-
       work interface card and the light on the network hub or switch port that the
       computer is connected to. If both are lit, the computer is connected to the
       network. If one or both aren’t lit, you have a connection problem. Several
       things may be wrong:
152   Is the Network Configuration Working?


          ✦ The patch cable that connects the computer to the wall outlet or that
            connects to the hub or switch may be bad. Replace it with one that you
            know is good in order to verify this problem.
          ✦ The cable run between the wall outlet and the patch panel may be bad.
            The cable may be physically broken, or it may be routed right next to a
            20,000-watt generator or an elevator motor.
          ✦ The computer’s NIC may be bad or configured incorrectly. Check the
            configuration settings. If necessary, replace the card.
          ✦ The hub or switch may be bad.



Is the Network Configuration Working?
         You can run three commands from a command window to verify the
         basic configuration of each computer. These commands are net config
         workstation, net config server, and ipconfig.

         The net config workstation command displays basic information
         about the computer’s network configuration. Here’s a sample of the output it
         displays:

         C:>net config workstation
         Computer name                        \\DOUG
         Full Computer name                   doug
         User name                            Doug Lowe
         Workstation active on
                 NetbiosSmb (000000000000)
                 NetBT_Tcpip_{FC6D2F39-FDDD-448E-9B3C-0C12847F2B61}
            (0050BA843911)
         Software version                     Windows 2002
         Workstation domain                   WORKGROUP
         Workstation Domain DNS Name          (null)
         Logon domain                         DOUG
         COM Open Timeout (sec)               0
         COM Send Count (byte)                16
         COM Send Timeout (msec)              250
         The command completed successfully.

         The most important information to check in the net config work
         station command’s output is the computer name and domain information.

         If the computer is configured to enable file and print sharing, you can also
         run net config server to display basic information about the server con-
         figuration. Here’s a sample of its output:
                       Is the Network Configuration Working?         153

C:>net config server
Server Name                           \\DOUG
Server Comment
Software version                      Windows 2002
Server is active on
        NetbiosSmb (000000000000)
        NetBT_Tcpip_{FB6D2F79-FDDF-418E-9B7C-0C82887F2A61}
   (0050ba843911)
Server hidden                         No
Maximum Logged On Users               5
Maximum open files per session        16384
Idle session time (min)               15
The command completed successfully.
                                                                                Book II
                                                                               Chapter 7
The ipconfig command displays information about the computer’s TCP/
IP configuration. If you type ipconfig by itself, the computer’s IP address,
subnet mask, and default gateway are displayed. If you type ipconfig /all,




                                                                               Your Network
                                                                                Installation
you see more detailed information. Here’s typical output from the ipconfig




                                                                                 Verifying
/all command:

C:>ipconfig /all
Windows IP Configuration
        Host Name . . . . . . . . . . .          .   :   doug
        Primary Dns Suffix . . . . . .           .   :
        Node Type . . . . . . . . . . .          .   :   Unknown
        IP Routing Enabled. . . . . . .          .   :   No
        WINS Proxy Enabled. . . . . . .          .   :   No
Ethernet adapter Local Area Connection:
        Connection-specific DNS Suffix           . : we1.client2.
   attbi.com
        Description . . . . . . . . . .          . : D-Link DFE-530TX+
   PCI Adapter
        Physical Address. . . . . . . .      00-50-BA-84-39-11
                                                 .   :
        Dhcp Enabled. . . . . . . . . .      Yes .   :
        Autoconfiguration Enabled . . .      Yes .   :
        IP Address. . . . . . . . . . .      192.168.1.100
                                                 .   :
        Subnet Mask . . . . . . . . . .      255.255.255.0
                                                 .   :
        Default Gateway . . . . . . . .      192.168.1.1
                                                 .   :
        DHCP Server . . . . . . . . . .      192.168.1.1
                                                 .   :
        DNS Servers . . . . . . . . . .      204.127.198.19
                                                 .   :
                                             63.240.76.19
         Lease Obtained. . . . . . . . . . : Saturday, May 24,
    2003 6:28:49 PM
         Lease Expires . . . . . . . . . . : Sunday, May 25,
    2003 6:28:49 PM

The most important information to glean from this output is the computer’s
IP address. You should also verify that the default gateway matches the IP
address of your Internet router and that the IP addresses for the DHCP and
DNS servers are correct.
154   Can the Computers Ping Each Other?


Can the Computers Ping Each Other?
         A basic test that you can perform to ensure that your network is function-
         ing is to use the ping command from a command prompt to make sure that
         the computers on the network can contact each other. The ping command
         simply sends a packet to another computer and requests that the second
         computer send a packet back in reply. If the reply packet is received, ping
         displays a message indicating how long it took to hear from the other com-
         puter. If the reply packet isn’t received, ping displays an error message indi-
         cating that the computer couldn’t be reached.

         You should try several ping tests. First, you can make sure that TCP/IP is
         up and running by having the computer try to ping itself. Open a command
         prompt and type ping 127.0.0.1. (127.0.0.1 is the standard loop-back address
         that a computer can use to refer to itself.) If you prefer, you can type ping
         localhost instead.

         Next, have the computer ping itself by using the IP address displayed by
         the \ ipconfig command. For example, if Ipconfig says the computer’s IP
         address is 192.168.0.100, type ping 192.168.0.100 at the command prompt.

         Now try to ping your servers. You’ll have to run ipconfig at each of the
         servers to determine their IP addresses. Or, you can just ping the comput-
         er’s name.

         A final test is to make sure that you can ping the workstation from other
         computers on the network. You don’t have to try to ping every computer
         from every other computer on the network unless you’ve determined that
         you have a connectivity problem that you need to pinpoint. However, you
         should try to ping each workstation from each of the servers, just to make
         sure the servers can see the workstations. Make a list of the IP addresses of
         the workstations as you test them and then take that list to the servers and
         ping each IP address on the list.



Can You Log On?
         After you’ve established that the basic network connections are working, the
         next step is to verify that network logon works. This is as simple as attempt-
         ing to log on from each computer by using the correct user account for the
         computer. If you can’t log on, several things may be causing the problem.
         Here are the most common:

          ✦ You may not have the right user account information. Double-check the
            username, password, and domain.
          ✦ Make sure that the domain name is correct.
                                             Do Network Printers Work?         155

        ✦ Passwords are case-sensitive. Make sure that you have typed the pass-
          word correctly and that the Caps Lock key isn’t on.
        ✦ You may not have a computer account for the computer. Double-check
          the computer name and make sure that you have a valid computer
          account on the server.
        ✦ Double-check the user account policies to make sure that there isn’t
          something that would prevent the user from logging on, such as a time-
          of-day restriction.



Are Network Drives Mapped Correctly?                                                       Book II
                                                                                          Chapter 7
       After you know the user can log on, you should make sure that mapped
       network drives are available. To do so, type net use at a command prompt.




                                                                                          Your Network
       You’ll see a list of all the network mappings. For example:




                                                                                           Installation

                                                                                            Verifying
       C:>net use
       New connections will be remembered.
       Status Local Remote              Network
       ---------------------------------------------------------------
       OK      M:     \\Doug\Prod       Microsoft Windows Network
       OK      X:     \\Doug\admin      Microsoft Windows Network
       OK      Z:     \\Doug\Marketing Microsoft Windows Network
       The command completed successfully.

       Here, you can see that three drives are mapped, and you can tell the server
       and share name for each mapped drive.

       Next, try to display a directory list of each drive to make sure that you can
       actually reach it. For example, type dir m:. If everything is working, you see a
       directory of the shared folder you’ve mapped to drive M:.



Do Network Printers Work?
       The final test I describe in this chapter is making sure that your network
       printers work. The easiest way to do this is to print a short document to the
       network printer and make sure that the document prints. I suggest that you
       open Notepad (choose Start➪Accessories➪Notepad), type a few words (like
       “Yo, Adrianne!”), and then choose File➪Print to bring up the Print dialog
       box. Select the network printer and click OK.

       If the network printer doesn’t appear in the list of available printers, go to
       the Printers and Faxes window and recheck the network printer. You may
       have incorrectly configured the printer. If the configuration looks okay, go to
       the printer itself and make sure that it’s turned on and ready to print.
156   Book II: Building a Network
       Chapter 8: Going Virtual
       In This Chapter
       ✓ Examining the basics of virtualization
       ✓ Weighing the benefits of virtualization
       ✓ Installing VMWare Player
       ✓ Creating and using virtual machines




       V    irtualization is one of the hottest trends in networking today.
            According to some industry pundits, virtualization is the best thing to
       happen to computers since the invention of the transistor. If you haven’t
       already begun to virtualize your network, you’re standing on the platform
       watching as the train is pulling out.

       This chapter is a brief introduction to virtualization, with an emphasis on
       using it to leverage your network server hardware to provide more servers
       using less hardware. In addition to the general concepts of virtualization,
       you find out how to experiment with virtualization using VMWare’s free vir-
       tualization product, called VMWare Player.

       Mastering a virtualization environment calls for a book of its own — I
       recommend Virtualization For Dummies by Bernard Golden or VMWare
       Infrastructure 3 For Dummies by William Lowe (no relation, honest).



Understanding Virtualization
       The basic idea behind virtualization is to use software to simulate the exis-
       tence of hardware. This powerful idea enables you to run more than one
       independent computer system on a single physical computer system. For
       example, suppose your organization requires a total of 12 servers to meet
       its needs. You could run each of these 12 servers on a separate computer,
       in which case you would have 12 computers in your server room. Or, you
       could use virtualization to run these 12 servers on just two computers. In
       effect, each of those computers would simulate six separate computer sys-
       tems, each running one of your servers.
158    Understanding Virtualization




                         The Roots of Virtualization
  Kids these days think they invented everything,    Each VM could run one of the various guest
  including virtualization.                          operating systems that were compatible with
                                                     the System/370 and appeared to this guest
  Little do they know.
                                                     operating system to be a complete, indepen-
  Virtualization was developed for PC-based          dent System/370 computer with its own pro-
  computers in the early 1990s, around the           cessor cores, virtual memory, disk partitions,
  time Captain Picard was flying the Enterprise      and input/output devices.
  around in Star Trek: The Next Generation.
                                                     The core of the VM system itself was called
  But the idea is much older than that.              the hypervisor, another term that persists to
                                                     this day.
  The first virtualized server computers predate
  Captain Picard by about 20 years. In 1972, IBM     The VM product IBM released in 1972 was
  released an operating system called simply VM      actually based on an experimental product
  which had nearly all of the basic features found   they released on a limited basis in 1967.
  in today’s virtualization products.
                                                     So whenever someone tells you about this
  VM allowed the administrators of IBM’s             new technology called virtualization, you can
  System/370 mainframe computers to create           tell them that it was invented when Star Trek
  multiple independent virtual machines, each        was on the air. When they ask, “you mean the
  of which was called (you guessed it) a virtual     one with Picard?” you can say, “No, the one
  machine or VM. This terminology is still in use    with Kirk.”
  today.



            Each of the simulated computers is called a virtual machine or VM. For all
            intents and purposes, each virtual machine appears to be a complete, self-
            contained computer system with its own processor (or, more likely, proces-
            sors), memory, disk drives, CD-ROM/DVD drives, keyboard, mouse, monitor,
            network interfaces, USB ports, and so on.

            Like a real computer, each virtual machine requires an operating system to
            do productive work. In a typical network server environment, each virtual
            machine runs its own copy of Windows Server 2008 (or an earlier version).
            The operating system has no idea that it’s running on a virtual machine
            rather than on a real machine.

            Here are a few terms you need to be familiar with if you expect to discuss
            virtualization intelligently:

             ✦ Host: The actual physical computer on which one or more virtual
               machines run.
                              Looking at the Benefits of Virtualization        159

        ✦ Bare Metal: Another term for the host computer that runs one or more
          virtual machines.
        ✦ Guest: Another term for a virtual machine running on a host.
        ✦ Guest Operating System: An operating system that runs within a virtual
          machine. By itself, a guest is just a machine; it requires an operating
          system to run. The guest operating system is what brings the guest to life.
           As far as licensing is concerned, Microsoft treats each virtual machine
           as a separate computer. Thus, if you run six guests on a single host and
           each guest runs Windows Server 2008, you need six licenses of Windows
           Server 2008.
                                                                                         Book II
        ✦ Hypervisor: The virtualization operating system that creates and runs
                                                                                        Chapter 8
          virtual machines.
           There are two basic types of hypervisors: Type 1 and Type 2. A Type 1




                                                                                              Going Virtual
           hypervisor is a hypervisor that itself runs directly on the bare metal. A
           Type 2 hypervisor is a hypervisor that runs within an operating system,
           which in turn runs on the bare metal.
           For production use, you should always use a Type 1 hypervisor because
           they’re much more efficient than Type 2 hypervisors. However, Type 1
           hypervisors are considerably more expensive than Type 2 hypervisors.
           As a result, many people use inexpensive or free Type 2 hypervisors to
           experiment with virtualization before making a commitment to purchase
           an expensive Type 1 hypervisor.



Looking at the Benefits of Virtualization
       You might suspect that virtualization is inefficient because a real computer
       is inherently faster than a simulated computer. Although it’s true that real
       computers are faster than simulated computers, virtualization technology
       has become so advanced that the performance penalty for running on a vir-
       tualized machine rather than a real machine is only a few percent.

       The small amount of overhead imposed by virtualization is usually more
       than made up for by the simple fact that even the most heavily utilized
       servers spend most of their time twiddling their digital thumbs, waiting for
       something to do. In fact, many servers spend nearly all of their time doing
       nothing. As computers get faster and faster, they spend even more of their
       time with nothing to do.

       Virtualization is a great way to put all of this unused processing power to
       good use.

       Besides this basic efficiency benefit, there are several other compelling ben-
       efits to virtualization:
160   Looking at the Benefits of Virtualization


          ✦ Hardware cost: You can typically save a lot of money by reducing
            hardware costs when you use virtualization. For example, suppose you
            replace ten servers that cost $4,000 each with one host server. Granted,
            you’ll probably spend more than $4,000 on that server, because it needs
            to be maxed out with memory, processor cores, network interfaces, and
            so on. So you’ll probably end up spending $15,000 or $20,000 for the
            host server. And you’ll end up spending something like $5,000 for the
            hypervisor software. But that’s still a lot less than the $40,000 you would
            have spent on ten separate computers at $4,000 each.
          ✦ Energy costs: Many organizations have found that going virtual has
            reduced their overall electricity consumption for server computers by
            80 percent. This savings is a direct result of using less computer hard-
            ware to do more work. For example, one host computer running ten vir-
            tual servers uses approximately one tenth of the energy used if each of
            the ten servers were run on separate hardware.
          ✦ Recoverability: One of the biggest benefits of virtualization is not the
            cost savings, but the ability to quickly recover from hardware failures.
            For example, suppose your organization has ten servers each running on
            separate hardware. If any one of those servers goes down due to a hard-
            ware failure — say a bad motherboard — that server will remain down
            until you can fix the computer. On the other hand, if those ten servers
            are running as virtual machines on two different hosts and one of the
            hosts fails, the virtual machines that were running on the failed host can
            be brought up on the other host in a matter of minutes.
             Granted, the servers will run less efficiently on a single host than they
             would have on two hosts, but the point is that they’ll all be running after
             only a short downtime.
             In fact, with the most advanced hypervisors available, the transfer from
             a failing host to another host can be done automatically and instanta-
             neously, so downtime is all but eliminated.
          ✦ Disaster recovery: Besides the benefit of recoverability when hardware
            failures occur, an even bigger benefit of virtualization comes into play in
            a true disaster recovery situation. For example, suppose your organiza-
            tion’s sever infrastructure consists of 20 separate servers. In the case of
            a devastating disaster, such as a fire in the server room that destroys all
            hardware, how long will it take you to get all 20 of those servers back up
            and running on new hardware? Quite possibly the recovery time will be
            measured in weeks.
             In contrast, virtual machines are actually nothing more than files that
             can be backed up onto tape. As a result, in a disaster-recovery situation,
             all you have to do is rebuild a single host computer and reinstall the
             hypervisor software. Then you can restore the virtual machine backups
             from tape, restart the virtual machines, and be back up and running in a
             matter of days instead of weeks.
                                               Getting Started with Virtualization       161

Getting Started with Virtualization
                  Virtualization is a complex subject, and mastering the ins and outs of work-
                  ing with a full-fledged virtualization system like VMWare Infrastructure is a
                  topic that’s beyond the scope of this book. However, you can dip your toes
                  into the shallow end of the virtualization pond by downloading and experi-
                  menting with VMWare’s free virtualization product, called VMWare Player.
                  You can download it from www.vmware.com.

                  Figure 8-1 shows VMWare Player’s main screen. From this screen, you can
                  create a new virtual machine or run one of the virtual machines you have
                  already created. As you can see, I’ve created two virtual machines so far:        Book II
                  one running Windows Server 2008 R2, the other running Linux.                     Chapter 8




                                                                                                         Going Virtual
Figure 8-1:
VMWare
Player
lets you
experiment
with
virtualization.



                  You can run an existing virtual machine by selecting the VM and clicking
                  Play Virtual Machine. This launches the virtual machine, which opens in a
                  new window, as shown in Figure 8-2. When you launch a virtual machine, the
                  VM behaves exactly as a real computer would when you power it up: First it
                  initializes its virtual hardware devices and then it loads the guest operating
                  system that has been installed in the VM. In the figure, Windows Server 2008
                  has booted up and is waiting for you to press Ctrl+Alt+Del to log on.

                  The prompt to press Ctrl+Alt+Del shown in Figure 8-2 illustrates one of the
                  peculiar details of running a virtual machine within a host operating system
                  (in this case, running Windows Server 2008 R2 within Windows 7 Ultimate):
                  When you press Ctrl+Alt+Del, which operating system — the host or the
                  guest — responds? The answer is that the host operating system responds
                  to the Ctrl+Alt+Del, so the guest operating system never sees it.
162     Creating a Virtual Machine




Figure 8-2:
A virtual
machine
running
Windows
Server 2008
R2.



              To get around this limitation, VMWare uses the special keyboard short-
              cut Ctrl+Alt+End to send a Ctrl+Alt+Del to the guest operating system.
              Alternatively, you can use the VM pull-down menu that appears in the menu
              bar above the virtual machine menu. This menu lists several actions that can
              be applied to the virtual machine, including Send Ctrl+Alt+Del.

              Another detail you should know about when working with a VM is that when
              you click in the virtual machine’s window, the VM captures your mouse
              and keyboard so that your input will be directed to the virtual machine
              rather than the host computer. If you want to break the bonds of the virtual
              machine and return to the host computer, press Ctrl and Alt.



Creating a Virtual Machine
              Creating a new virtual machine in VMWare Player is relatively easy. In fact,
              the most challenging part is that you’ll need the installation disk for the
              operating system you want to install on the VM. Remember that a virtual
              machine is useless without a guest operating system, so you need to have
              the installation disk available before you create the virtual machine.
                                                    Creating a Virtual Machine         163

              If you just want to experiment with virtualization and don’t have extra
              licenses of a Windows server operating system, you can always download
              an evaluation copy of Windows Server 2008 R2 from www.microsoft.com/
              windowsserver2008. The evaluation period is six months, so you’ll have
              plenty of time to experiment.

              The downloadable trial version of Windows Server 2008 R2 comes in the
              form of an .iso file, which is an image of a DVD file that you can mount
              within your virtual machine as if it were a real disk.

              Once you have your .iso file or installation disk ready to go, you can create a
              new virtual machine by following these steps:
                                                                                                 Book II
                                                                                                Chapter 8
              1. Click Create a New Virtual Machine from the VMWare Player home
                  screen.




                                                                                                      Going Virtual
                  This brings up the New Virtual Machine Wizard, as shown in Figure 8-3.




Figure 8-3:
The first
page of the
New Virtual
Machine
Wizard.



              2. Choose the installation option you want to use.
                  There are three choices:
                   • Select Installer Disc and then choose the drive you will install from if
                     you want to install from an actual CD or DVD.
                   • Select Install Disc Image File (iso) and then click the Browse button
                     and browse to the iso file for the operating system installation disc if
                     you want to install from an iso file.
                   • Select I Will Install the Operating System Later if you want to create
                     the virtual machine but install the operating system later.
164      Creating a Virtual Machine


                  Note that the remaining steps in this procedure assume that you
                  selected a Windows Server 2008 R2 iso file as the installation option.
               3. Click Next.
                  The screen shown in Figure 8-4 appears. You can enter the product key
                  now or skip this step until later.




Figure 8-4:
The New
Virtual
Machine
Wizard asks
for your
product key.



               4. If you have the Windows product key, enter it and click Next.
                  Otherwise just click Next.
                  You can always enter the product key later if you don’t have it handy
                  now. Either way, the screen shown in Figure 8-5 appears next.




Figure 8-5:
Creating a
name and
specifying
the VM disk
location.
                                                   Creating a Virtual Machine         165

               5. Enter a name for the virtual machine.
               6. Enter the location for the virtual machine’s disk file.
                  If you want, you can click the Browse button and browse to the folder
                  where you want to create the file.
               7. Click Next.
                  The Wizard asks for the size of the disk to create for the virtual machine,
                  as shown in Figure 8-6.


                                                                                                 Book II
                                                                                                Chapter 8




                                                                                                      Going Virtual
Figure 8-6:
Specifying
the VM disk
size.



               8. Set the size of the virtual machine’s hard drive.
                  The default setting is 40GB, but you can change this depending on your
                  needs. Note that you must have sufficient space available on the host
                  computer’s disk drive.
               9. Click Next.
                  The Wizard displays a final confirmation page, as shown in Figure 8-7.
              10. Click Finish.
                  The Wizard creates the virtual machine and then starts it. Because the
                  machine doesn’t have an operating system installed, it boots from the
                  CD/DVD installation image you specified back in Step 2. In this case,
                  I booted with the Windows Server 2008 R2 evaluation software disk
                  image, so the new virtual machine displays the Install Windows screen,
                  as shown in Figure 8-8.
166      Creating a Virtual Machine




Figure 8-7:
VMWare
is ready
to create
the virtual
machine.




Figure 8-8:
Installing
Windows
Server
2008 R2 in
a virtual
machine.



              11. Follow the steps to install the operating system.
                  Installing an operating system in a virtual machine is exactly the same as
                  installing it on a physical computer, except that the installation screens
                  appear within a virtual machine window.
                                                   Creating a Virtual Machine         167

              12. You’re done!
                  When the operating system is installed, you can then proceed to use the
                  virtual machine.

              You can adjust the hardware configuration of a virtual machine by choosing
              VM➪Settings while the virtual machine is running. This brings up the Virtual
              Machine Settings dialog box, as shown in Figure 8-9. From this dialog box,
              you can adjust the virtual machine’s hardware configuration including the
              amount of RAM available to the VM and the number of processor cores. You
              can also adjust the disk drive size, add CD, DVD, or floppy drives, and config-
              ure network adapters, USB connections, and sound and display settings.
                                                                                                 Book II
                                                                                                Chapter 8




                                                                                                      Going Virtual
Figure 8-9:
Configuring
virtual
machine
settings.
168   Book II: Building a Network
        Book III
Network Administration
    and Security
Contents at a Glance
      Chapter 1: Help Wanted: Job Description for
      a Network Administrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .171

      Chapter 2: Security 101 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185

      Chapter 3: Managing User Accounts . . . . . . . . . . . . . . . . . . . . . . . . . . .195

      Chapter 4: Firewalls and Virus Protection. . . . . . . . . . . . . . . . . . . . . . .203

      Chapter 5: Extending Your Network with VPN Access. . . . . . . . . . . .215

      Chapter 6: Managing Network Software. . . . . . . . . . . . . . . . . . . . . . . .221

      Chapter 7: Solving Network Problems . . . . . . . . . . . . . . . . . . . . . . . . . .233

      Chapter 8: Network Performance Anxiety. . . . . . . . . . . . . . . . . . . . . . .249

      Chapter 9: Backing Up Your Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .259

      Chapter 10: Disaster Recovery and Business Continuity Planning 271s
      Chapter 1: Help Wanted: Job
      Description for a Network
      Administrator
      In This Chapter
      ✓ Deciphering the many jobs of the network administrator
      ✓ Dusting, vacuuming, and mopping
      ✓ Managing the network users
      ✓ Choosing the right tools
      ✓ Getting certified




      H       elp wanted. Network administrator to help small business get control of
              a network run amok. Must have sound organizational and management
      skills. Only moderate computer experience required. Part time only.

      Does this ad sound like one that your company should run? Every network
      needs a network administrator, whether the network has 2 computers or
      200. Of course, managing a 200-computer network is a full-time job, whereas
      managing a 2-computer network isn’t. At least, it shouldn’t be.

      This chapter introduces you to the boring job of network administration.
      Oops . . . you’re probably reading this chapter because you’ve been elected
      to be the network manager, so I’d better rephrase that: This chapter intro-
      duces you to the wonderful, exciting world of network management! Oh,
      boy! This is going to be fun!



Knowing What Network Administrators Do
      Simply put, network administrators administer networks, which means that
      they take care of the tasks of installing, configuring, expanding, protecting,
      upgrading, tuning, and repairing the network. Network administrators take
      care of the network hardware, such as cables, hubs, switches, routers, serv-
      ers, and clients, as well as network software, such as network operating
      systems, e-mail servers, backup software, database servers, and application
      software. Most importantly, network administrators take care of network
      users by answering their questions, listening to their troubles, and solving
      their problems.
172   Knowing What Network Administrators Do


         On a big network, these responsibilities constitute a full-time job. Large net-
         works tend to be volatile: Users come and go, equipment fails, cables break,
         and life in general seems to be one crisis after another.

         Smaller networks are much more stable. After you get your network up and
         running, you probably won’t have to spend much time managing its hard-
         ware and software. An occasional problem may pop up, but with only a few
         computers on the network, problems should be few and far between.

         Regardless of the network’s size, all network administrators must attend to
         several common chores:

          ✦ Equipment upgrades: The network administrator should be involved
            in every decision to purchase new computers, printers, or other equip-
            ment. In particular, the network administrator should be prepared to
            lobby for the most network-friendly equipment possible, such as new
            computers that already have network cards installed and configured and
            printers that are network ready.
          ✦ Configuration: The network administrator must put on the pocket
            protector whenever a new computer is added to the network. The net-
            work administrator’s job includes considering what changes to make
            to the cabling configuration, what computer name to assign to the new
            computer, how to integrate the new user into the security system, what
            rights to grant the user, and so on.
          ✦ Software upgrades: Every once in a while, your trusty operating system
            vendor (in other words, Microsoft) releases a new version of your net-
            work operating system. The network administrator must read about the
            new version and decide whether its new features are beneficial enough to
            warrant an upgrade. In most cases, the hardest part of upgrading to a new
            version of your network operating system is determining the migration
            path — that is, how to upgrade your entire network to the new version
            while disrupting the network or its users as little as possible. Upgrading to
            a new network operating system version is a major chore, so you need to
            carefully consider the advantages that the new version can bring.
          ✦ Patches: Between upgrades, Microsoft releases patches and service
            packs that fix minor problems with its server operating systems. For
            more information, see the section “Patching Up Your Operating System
            and Software” later in this chapter.
          ✦ Performance maintenance: One of the easiest traps that you can get
            sucked into is the quest for network speed. The network is never fast
            enough, and users always blame the hapless network manager. So the
            administrator spends hours and hours tuning and tweaking the network
            to squeeze out that last 2 percent of performance. You don’t want to get
            caught in this trap, but in case you do, Chapter 8 of this book can help. It
            clues you in to the basics of tuning your network for best performance.
                                Choosing the Part-Time Administrator         173

        ✦ Ho-hum chores: Network administrators perform routine chores, such
          as backing up the servers, archiving old data, freeing up server hard
          drive space, and so on. Much of network administration is making sure
          that things keep working and finding and correcting problems before
          any users notice that something is wrong. In this sense, network admin-
          istration can be a thankless job.
        ✦ Software inventory: Network administrators are also responsible for
          gathering, organizing, and tracking the entire network’s software inven-
          tory. You never know when something is going to go haywire on Joe in
          Marketing’s ancient Windows 2000 computer and you’re going to have to
          reinstall that old copy of WordPerfect. Do you have any idea where the
          installation discs are?



Choosing the Part-Time Administrator
       The larger the network, the more technical support it needs. Most small
       networks — with just a dozen or two computers — can get by with a part-
       time network administrator. Ideally, this person should be a closet computer
       geek: someone who has a secret interest in computers but doesn’t like to
       admit it. Someone who will take books home with him or her and read them
       over the weekend. Someone who enjoys solving computer problems just for
       the sake of solving them.                                                        Book III
                                                                                       Chapter 1
       The job of managing a network requires some computer skills, but it isn’t




                                                                                       Network Administrator
       entirely a technical job. Much of the work that the network administrator




                                                                                         Help Wanted: Job
                                                                                         Description for a
       does is routine housework. Basically, the network administrator dusts, vacu-
       ums, and mops the network periodically to keep it from becoming a mess.

       Here are some additional ideas on picking a part-time network administrator:

        ✦ The network administrator needs to be an organized person. Conduct a
          surprise office inspection and place the person with the neatest desk in
          charge of the network. (Don’t warn them in advance, or everyone may
          mess up their desks intentionally the night before the inspection.)
        ✦ Allow enough time for network administration. For a small network (say,
          no more than 20 or so computers), an hour or two each week is enough.
          More time is needed upfront as the network administrator settles into
          the job and discovers the ins and outs of the network. After an initial
          settling-in period, though, network administration for a small office net-
          work doesn’t take more than an hour or two per week. (Of course, larger
          networks take more time to manage.)
        ✦ Make sure that everyone knows who the network administrator is and
          that the network administrator has the authority to make decisions about
          the network, such as what access rights each user has, what files can and
          can’t be stored on the server, how often backups are done, and so on.
174   Establishing Routine Chores


          ✦ Pick someone who is assertive and willing to irritate people. A good net-
            work administrator should make sure that backups are working before a
            hard drive fails and make sure that antivirus protection is in place before
            a virus wipes out the entire network. This policing will irritate people,
            but it’s for their own good.
          ✦ In most cases, the person who installs the network is also the network
            administrator. This is appropriate because no one understands the net-
            work better than the person who designs and installs it.
          ✦ The network administrator needs an understudy — someone who knows
            almost as much about the network, is eager to make a mark, and smiles
            when the worst network jobs are delegated.
          ✦ The network administrator has some sort of official title, such as
            Network Boss, Network Czar, Vice President in Charge of Network
            Operations, or Dr. Network. A badge, a personalized pocket protector,
            or a set of Spock ears helps, too.



Establishing Routine Chores
         Much of the network administrator’s job is routine stuff — the equivalent
         of vacuuming, dusting, and mopping. Or if you prefer, changing the oil and
         rotating the tires every 3,000 miles. Yes, it’s boring, but it has to be done.

          ✦ Backup: The network administrator needs to make sure that the net-
            work is properly backed up. If something goes wrong and the network
            isn’t backed up, guess who gets the blame? On the other hand, if
            disaster strikes, yet you’re able to recover everything from yesterday’s
            backup with only a small amount of work lost, guess who gets the pat
            on the back, the fat bonus, and the vacation in the Bahamas? Chapter 9
            of this book describes the options for network backups. You’d better
            read it soon.
          ✦ Protection: Another major task for network administrators is sheltering
            your network from the evils of the outside world. These evils come in
            many forms, including hackers trying to break into your network and
            virus programs arriving through e-mail. Chapter 4 of this book describes
            this task in more detail.
          ✦ Cleanup: Users think that the network server is like the attic: They want
            to throw files up there and leave them forever. No matter how much
            storage your network has, your users will fill it up sooner than you think.
            So the network manager gets the fun job of cleaning up the attic once
            in a while. Oh, joy. The best advice I can offer is to constantly complain
            about how messy it is up there and warn your users that spring cleaning
            is coming up.
                 Patching Up Your Operating System and Software              175

Managing Network Users
      Managing network technology is the easiest part of network management.
      Computer technology can be confusing at first, but computers aren’t nearly
      as confusing as people. The real challenge of managing a network is manag-
      ing the network’s users.

      The difference between managing technology and managing users is obvi-
      ous: You can figure out computers, but you can never really figure out
      people. The people who use the network are much less predictable than the
      network itself. Here are some tips for dealing with users:

       ✦ Training is a key part of the network manager’s job. Make sure that
         everyone who uses the network understands it and knows how to use
         it. If the network users don’t understand the network, they may uninten-
         tionally do all kinds of weird things to it.
       ✦ Never treat your network users like they’re idiots. If they don’t under-
         stand the network, it isn’t their fault. Explain it to them. Offer a class.
         Buy them each a copy of Networking All-in-One For Dummies and tell
         them to read it during their lunch hour. Hold their hands. But don’t treat
         them like idiots.
       ✦ Make up a network cheat sheet that contains everything that the users          Book III
         need to know about using the network on one page. Make sure that              Chapter 1
         everyone gets a copy.




                                                                                       Network Administrator
       ✦ Be as responsive as possible when a network user complains of a net-




                                                                                         Help Wanted: Job
                                                                                         Description for a
         work problem. If you don’t fix the problem soon, the user may try to fix
         it. You probably don’t want that.
       ✦ The better you understand the psychology of network users, the more
         prepared you’ll be for the strangeness they often serve up. Toward that
         end, I recommend that you read the Diagnostic and Statistical Manual of
         Mental Disorders (also known as DSM-IV) cover to cover.


Patching Up Your Operating System and Software
      One of the annoyances that every network manager faces is applying soft-
      ware patches to keep your operating system and other software up to date.
      A software patch is a minor update that fixes small glitches that crop up
      from time to time, such as minor security or performance issues. These
      glitches aren’t significant enough to merit a new version of the software,
      but they’re important enough to require fixing. Most of the patches correct
      security flaws that computer hackers have uncovered in their relentless
      attempts to prove that they’re smarter than the security programmers at
      Microsoft.
176   Discovering Software Tools for Network Administrators


         Periodically, all the recently released patches are combined into a service
         pack. Although the most diligent network administrators apply all patches as
         they’re released, many administrators just wait for the service packs.

         For all versions of Windows, you can use Windows Update to apply patches
         to keep your operating system and other Microsoft software up to date. You
         can find Windows Update in the Start menu. Or, you can fire up Internet
         Explorer and browse to http://update.microsoft.com. Windows
         Update automatically scans your computer’s software and creates a list of
         software patches and other components that you can download and install.
         You can also configure Windows Update to automatically notify you of
         updates so that you don’t have to remember to check for new patches.

         For larger networks, you can set up a server that runs Microsoft’s Software
         Update Services (SUS) to automate software updates. SUS essentially lets
         you set up your own Windows Update site on your own network. Then, you
         have complete control over how software updates are delivered to the com-
         puters on your network. For more information, see www.microsoft.com/
         windowsserversystem/updateservices.



Discovering Software Tools for Network Administrators
         Network administrators need certain tools to get their jobs done. Adminis-
         trators of big, complicated, and expensive networks need big, complicated,
         and expensive tools. Administrators of small networks need small tools.

         Some of the tools that the administrator needs are hardware tools, such as
         screwdrivers, cable crimpers, and hammers. The tools that I’m talking about
         here, however, are software tools. Here’s a sampling of the tools you’ll need:

          ✦ A diagramming tool: A diagramming tool lets you draw pictures of your
            network. Microsoft sells a program called Visio that’s specially designed
            for the types of diagrams you’ll want to make as a network administrator.
          ✦ A network discovery program: For larger networks, you may want
            to invest in a network discovery program such as NetworkView (www.
            networkview.com) that can automatically document your network’s
            structure for you. These programs scan the network carefully, looking
            for computers, printers, routers, and other devices. They then create a
            database of the network components, draw diagrams for you, and chug
            out helpful reports.
          ✦ The network’s built-in tools: Many of the software tools that you need
            to manage a network come with the network itself. As the network
            administrator, you should read through the manuals that come with
            your network software to see what management tools are available. For
            example, Windows includes a net diag command that you can use to
            make sure that all the computers on a network can communicate with
       Discovering Software Tools for Network Administrators                 177

   each other. (You can run net diag from an MS-DOS prompt.) For TCP/
   IP networks, you can use the TCP/IP diagnostic commands summarized
   in Table 1-1. For more information about these commands, check out
   Book IV, Chapter 6.


 Table 1-1                  TCP/IP Diagnostic Commands
 Command           What It Does
 arp               Displays address resolution information used by the Address
                   Resolution Protocol (ARP).
 hostname          Displays your computer’s host name.
 ipconfig          Displays current TCP/IP settings.
 nbtstat           Displays the status of NetBIOS over TCP/IP connections.
 netstat           Displays statistics for TCP/IP.
 nslookup          Displays DNS information.
 ping              Verifies that a specified computer can be reached.
 route             Displays the PC’s routing tables.
 tracert           Displays the route from your computer to a specified host.
                                                                                    Book III
                                                                                   Chapter 1
✦ System Information: The System Information program that comes with




                                                                                   Network Administrator
  Windows is a useful utility for network managers.




                                                                                     Help Wanted: Job
                                                                                     Description for a
✦ Hotfix Checker: Another handy tool available from Microsoft is the
  Hotfix Checker, which scans your computers to see what patches need
  to be applied. You can download the Hotfix Checker free of charge from
  Microsoft’s Web site. Just go to www.microsoft.com and search for
  hfnetchk.exe.
✦ Microsoft Baseline Security Analyzer: If you prefer GUI-based tools,
  check out Microsoft Baseline Security Analyzer. You can download it
  from Microsoft’s Web site free of charge. To find it, go to www.micro
  soft.com and search for Microsoft Baseline Security Analyzer.
✦ A utility program: I suggest that you get one of those 100-in-1 utility
  programs, such as Symantec’s Norton Utilities. Norton Utilities includes
  invaluable utilities for repairing damaged hard drives, rearranging the
  directory structure of your hard drive, gathering information about your
  computer and its equipment, and so on.
   Never use a hard drive repair program that wasn’t designed to work
   with the operating system or version that your computer uses or the file
   system you’ve installed. Any time that you upgrade to a newer version of
   your operating system, you should also upgrade your hard drive repair
   programs to a version that supports the new operating system version.
178   Building a Library


          ✦ A protocol analyzer: A protocol analyzer is a program that’s designed to
            monitor and log the individual packets that travel along your network.
            (Protocol analyzers are also called packet sniffers.) You can configure
            the protocol analyzer to filter specific types of packets, watch for spe-
            cific types of problems, and provide statistical analysis of the captured
            packets. Most network administrators agree that Sniffer, by Network
            General (www.networkgeneral.com), is the best protocol analyzer
            available. However, it’s also one of the most expensive. If you prefer a
            free alternative, check out Ethereal, which you can download free from
            www.ethereal.com.
          ✦ Network Monitor: All current versions of Windows include a program
            called Network Monitor that provides basic protocol analysis and can
            often help solve pesky network problems.



Building a Library
         One of Scotty’s best lines in the original Star Trek series was when he
         refused to take shore leave so he could get caught up on his technical jour-
         nals. “Don’t you ever relax?” asked Kirk. “I am relaxing!” Scotty replied.

         To be a good network administrator, you need to read computer books. Lots
         of them. And you need to enjoy doing it. If you’re the type who takes computer
         books with you to the beach, you’ll make a great network administrator.

         You need books on a variety of topics. I’m not going to recommend specific
         titles, but I do recommend that you get a good, comprehensive book on each
         of the following topics:

          ✦ Network security and hacking
          ✦ Wireless networking
          ✦ Network cabling and hardware
          ✦ Ethernet
          ✦ Windows Server 2003 or 2008
          ✦ Windows XP or Vista
          ✦ Linux
          ✦ TCP/IP
          ✦ DNS and BIND
          ✦ Sendmail
          ✦ Exchange Server
                                                         Getting Certified     179

       In addition to books, you may also want to subscribe to some magazines to
       keep up with what’s happening in the networking industry. Here are a few
       you should probably consider, along with their Web addresses:

        ✦ InformationWeek: www.informationweek.com
        ✦ InfoWorld: www.infoworld.com
        ✦ Network Computing: www.networkcomputing.com
        ✦ Network World: www.networkworld.com
        ✦ 2600 (a great magazine on computer hacking and security):
          www.2600.com

       The Internet is one of the best sources of technical information for network
       administrators. You’ll want to stock your browser’s Favorites menu with
       plenty of Web sites that contain useful networking information. In addi-
       tion, you may want to subscribe to one of the many online newsletters that
       deliver fresh information on a regular basis via e-mail.



Getting Certified
       Remember the scene near the end of The Wizard of Oz when the Wizard
                                                                                       Book III
       grants the Scarecrow a diploma, the Cowardly Lion a medal, and the Tin Man
                                                                                      Chapter 1
       a testimonial?




                                                                                      Network Administrator

                                                                                        Help Wanted: Job
                                                                                        Description for a
       Network certifications are kind of like that. I can picture the scene now:

           The Wizard: “And as for you, my network-burdened friend, any geek with
           thick glasses can administer a network. Back where I come from, there
           are people who do nothing but configure Cisco routers all day long.
           And they don’t have any more brains than you do. But they do have one
           thing you don’t have: certification. And so, by the authority vested in
           me by the Universita Committeeatum E Pluribus Unum, I hereby confer
           upon you the coveted certification of CND.”
           You: “CND?”
           The Wizard: “Yes, that’s, uh, Certified Network Dummy.”
           You: “The Seven Layers of the OSI Reference Model are equal to the Sum
           of the Layers on the Opposite Side. Oh, rapture! I feel like a network
           administrator already!”

       My point is that certification in and of itself doesn’t guarantee that you
       really know how to administer a network. That ability comes from real-
       world experience — not exam crams.
180   Getting Certified


         Nevertheless, certification is becoming increasingly important in today’s
         competitive job market. So you may want to pursue certification — not just
         to improve your skills, but also to improve your resume. Certification is
         an expensive proposition. Each test can cost several hundred dollars, and
         depending on your technical skills, you may need to buy books to study or
         enroll in training courses before you take the tests.

         You can pursue two basic types of certification: vendor-specific certifica-
         tion and vendor-neutral certification. The major software vendors such as
         Microsoft and Cisco provide certification programs for their own equipment
         and software. CompTIA, a nonprofit industry trade association, provides the
         best-known vendor-neutral certification.

         The following sections describe some of the certifications offered by
         CompTIA, Microsoft, Novell, and Cisco.


         CompTIA
         www.comptia.org

          ✦ A+ is a basic certification for an entry-level computer technician. To
            attain A+ certification, you have to pass two exams: one on computer
            hardware, the other on operating systems.
          ✦ Linux+ covers basic Linux skills such as installation, operations, and
            troubleshooting. This certification is vendor neutral, so it doesn’t
            depend on any particular version of Linux.
          ✦ Network+ is a popular vendor-neutral networking certification. It covers
            four major topic areas: Media and Topologies, Protocols and Standards,
            Network Implementation, and Network Support.
          ✦ Server+ covers network server hardware. It includes details such as
            installing and upgrading server hardware, installing and configuring a
            NOS, and so on.
          ✦ Security+ is for security specialists. The exam topics include general
            security concepts, communication security, infrastructure security,
            basics of cryptography, and operational/organizational security.


         Microsoft
         www.microsoft.com/learning/mcp

          ✦ MCTS, or Microsoft Certified Technology Specialist, is a certification in a
            specific Microsoft technology or product.
          ✦ MCITP, or Microsoft Certified IT Professional, is a certification in deploy-
            ing and maintaining IT infrastructure.
                                                   Gurus Need Gurus, Too          181

        ✦ MCSE, or Microsoft Certified Systems Engineer, is a prestigious certifica-
          tion for networking professionals who design and implement networks.
          To gain this certification, you have to pass a total of seven exams.
          Microsoft offers separate Windows 2000 Server and Windows Server
          2003 certification tracks.
        ✦ MCSA, or Microsoft Certified System Administrator, is for networking
          professionals who administer existing networks.


       Cisco
       www.cisco.com/certification

        ✦ CCNA, or Cisco Certified Network Associate, is an entry-level apprentice
          certification. A CCNA should be able to install, configure, and operate
          Cisco equipment for small networks (under 100 nodes).
        ✦ CCNP, or Cisco Certified Network Professional, is a professional-level
          certification for Cisco equipment. A CCNP should be able to install, con-
          figure, and troubleshoot Cisco networks of virtually any size.
        ✦ CCDA, or Cisco Certified Design Associate, is an entry-level certification
          for network design.
        ✦ CCDP, or Cisco Certified Design Professional, is for network design pro-
          fessionals. Both the CCDA and CCNA certifications are prerequisites for          Book III
          the CCDP.                                                                       Chapter 1




                                                                                          Network Administrator
        ✦ CCIP, or Cisco Certified Internetwork Professional, is a professional-level




                                                                                            Help Wanted: Job
                                                                                            Description for a
          certification that emphasizes advanced use of IP and related protocols
          to create intranetworks.
        ✦ CCIE, or Cisco Certified Internetwork Expert, is the top dog of Cisco
          certifications.
        ✦ And much more! There are many more Cisco certifications to choose
          from, including certification for security, voice technology, wireless net-
          working, and more.



Gurus Need Gurus, Too
       No matter how much you know about computers, plenty of people know
       more than you do. This rule seems to apply at every rung of the ladder of
       computer experience. I’m sure that a top rung exists somewhere, occupied
       by the world’s best computer guru. However, I’m not sitting on that rung,
       and neither are you. (Not even Bill Gates is sitting on that rung. In fact, Bill
       Gates got to where he is today by hiring people on higher rungs.)
182   Helpful Bluffs and Excuses


         As the local computer guru, one of your most valuable assets can be a
         knowledgeable friend who’s a notch or two above you on the geek scale.
         That way, when you run into a real stumper, you have a friend to call for
         advice. Here are some tips for handling your own guru:

          ✦ In dealing with your own guru, don’t forget the Computer Geek’s Golden
            Rule: “Do unto your guru as you would have your own users do unto
            you.” Don’t pester your guru with simple stuff that you just haven’t
            spent the time to think through. If you have thought it through and can’t
            come up with a solution, however, give your guru a call. Most computer
            experts welcome the opportunity to tackle an unusual computer prob-
            lem. It’s a genetic defect.
          ✦ If you don’t already know someone who knows more about computers
            than you do, consider joining your local PC users’ group. The group
            may even have a subgroup that specializes in your networking software
            or may be devoted entirely to local folks who use the same networking
            software that you use. Odds are good that you’re sure to make a friend
            or two at a users’ group meeting. Also, you can probably convince your
            boss to pay any fees required to join the group.
          ✦ If you can’t find a real-life guru, try to find an online guru. Check out
            the various computing newsgroups on the Internet. Subscribe to online
            newsletters that are automatically delivered to you via e-mail.



Helpful Bluffs and Excuses
         As network administrator, you just won’t be able to solve a problem some-
         times, at least not immediately. You can do two things in this situation. The
         first is to explain that the problem is particularly difficult and that you’ll
         have a solution as soon as possible. The second solution is to look the user
         in the eyes and, with a straight face, try one of these phony explanations:

          ✦ Blame it on the version of whatever software you’re using. “Oh, they
            fixed that with version 39.”
          ✦ Blame it on cheap, imported memory chips.
          ✦ Blame it on Democrats. Or Republicans. Or hanging chads. Whatever.
          ✦ Blame it on oil company executives.
          ✦ Blame it on global warming.
          ✦ Hope that the problem wasn’t caused by stray static electricity. Those
            types of problems are very difficult to track down. Tell your users that
            not properly discharging themselves before using their computers can
            cause all kinds of problems.
                                  Helpful Bluffs and Excuses    183

✦ You need more memory.
✦ You need a bigger hard drive.
✦ You need a faster processor.
✦ Blame it on Jar-Jar Binks.
✦ You can’t do that in Windows Vista.
✦ You can only do that in Windows Vista.
✦ Could be a virus.
✦ Or sunspots.
✦ No beer and no TV make Homer something something something. . . .




                                                                       Book III
                                                                      Chapter 1




                                                                      Network Administrator

                                                                        Help Wanted: Job
                                                                        Description for a
184   Book III: Network Administration and Security
Chapter 2: Security 101
In This Chapter
✓ Assessing the risk for security
✓ Determining your basic security philosophy
✓ Physically securing your network equipment
✓ Figuring out user account security
✓ Using other network security techniques




B    efore you had a network, computer security was easy. You simply
     locked your door when you left work for the day. You could rest easy,
secure in the knowledge that the bad guys would have to break down the
door to get to your computer.

The network changes all that. Now, anyone with access to any computer on
the network can break into the network and steal your files. Not only do you
have to lock your door, but you also have to make sure that other people
lock their doors, too.

Fortunately, network operating systems have built-in provisions for network
security. This situation makes it difficult for someone to steal your files,
even if they do break down the door. All modern network operating systems
have security features that are more than adequate for all but the most
paranoid users.

When I say more than adequate, I mean it. Most networks have security
features that would make even Maxwell Smart happy. Using all these secu-
rity features is kind of like Smart insisting that the Chief lower the “Cone of
Silence.” The Cone of Silence worked so well that Max and the Chief couldn’t
hear each other! Don’t make your system so secure that even the good guys
can’t get their work done.

If any of the computers on your network are connected to the Internet, you
have to contend with a whole new world of security issues. For more infor-
mation about Internet security, see Chapter 4 of this minibook. Also, if your
network supports wireless devices, you have to contend with wireless secu-
rity issues. For more information about security for wireless networks, see
Book V, Chapter 2.
186   Do You Need Security?


Do You Need Security?
         Most small networks are in small businesses or departments where every-
         one knows and trusts everyone else. Folks don’t lock up their desks when
         they take a coffee break, and although everyone knows where the petty cash
         box is, money never disappears.

         Network security isn’t necessary in an idyllic setting like this one, is it? You
         bet it is. Here’s why any network should be set up with at least some mini-
         mal concern for security:

          ✦ Even in the friendliest office environment, some information is and
            should be confidential. If this information is stored on the network, you
            want to store it in a directory that’s available only to authorized users.
          ✦ Not all security breaches are malicious. A network user may be rou-
            tinely scanning through his or her files and come across a filename that
            isn’t familiar. The user may then call up the file, only to discover that it
            contains confidential personnel information, juicy office gossip, or your
            résumé. Curiosity, rather than malice, is often the source of security
            breaches.
          ✦ Sure, everyone at the office is trustworthy now. However, what if some-
            one becomes disgruntled, a screw pops loose, and he or she decides to
            trash the network files before jumping out the window? What if someone
            decides to print a few $1,000 checks before packing off to Tahiti?
          ✦ Sometimes the mere opportunity for fraud or theft can be too much for
            some people to resist. Give people free access to the payroll files, and
            they may decide to vote themselves a raise when no one is looking.
          ✦ If you think that your network doesn’t contain any data that would be
            worth stealing, think again. For example, your personnel records prob-
            ably contain more than enough information for an identity thief: names,
            addresses, phone numbers, Social Security numbers, and so on. Also,
            your customer files may contain your customers’ credit card numbers.
          ✦ Hackers who break into your network may not be interested in stealing
            your data. Instead, they may be looking to plant a Trojan horse program
            on your server, which enables them to use your server for their own
            purposes. For example, someone may use your server to send thou-
            sands of unsolicited spam e-mail messages. The spam won’t be traced
            back to the hackers; it will be traced back to you.
          ✦ Finally, remember that not everyone on the network knows enough
            about how Windows and the network work to be trusted with full access
            to your network’s data and systems. One careless mouse click can wipe
            out an entire directory of network files. One of the best reasons for acti-
            vating your network’s security features is to protect the network from
            mistakes made by users who don’t know what they’re doing.
                                Physical Security: Locking Your Doors           187

Considering Two Approaches to Security
       When you’re planning how to implement security on your network, you
       should first consider which of two basic approaches to security you will take:

        ✦ An open-door type of security, in which you grant everyone access to
          everything by default and then place restrictions just on those resources
          to which you want to limit access.
        ✦ A closed-door type of security, in which you begin by denying access to
          everything and then grant specific users access to the specific resources
          that they need.

       In most cases, the open-door policy is easier to implement. Typically, only a
       small portion of the data on a network really needs security, such as confi-
       dential employee records or secrets such as the Coke recipe. The rest of the
       information on a network can be safely made available to everyone who can
       access the network.

       If you choose the closed-door approach, you set up each user so that he or
       she has access to nothing. Then, you grant each user access only to those
       specific files or folders that he or she needs.

       The closed-door approach results in tighter security, but can lead to the           Book III
       Cone of Silence Syndrome: Like Max and the Chief who can’t hear each other         Chapter 2
       talk while they’re under the Cone of Silence, your network users will con-
       stantly complain that they can’t access the information that they need. As a




                                                                                                Security 101
       result, you’ll find yourself frequently adjusting users’ access rights. Choose
       the closed-door approach only if your network contains a lot of information
       that is very sensitive, and only if you’re willing to invest time administrating
       your network’s security policy.

       You can think of the open-door approach as an entitlement model, in which
       the basic assumption is that users are entitled to network access. In con-
       trast, the closed-door policy is a permissions model, in which the basic
       assumption is that users aren’t entitled to anything but must get permission
       for every network resource that they access.



Physical Security: Locking Your Doors
       The first level of security in any computer network is physical security. I’m
       amazed when I walk into the reception area of an accounting firm and see
       an unattended computer sitting on the receptionist’s desk. As often as not,
       the receptionist has logged on to the system and then walked away from the
       desk, leaving the computer unattended.
188   Physical Security: Locking Your Doors


         Physical security is important for workstations but vital for servers. Any
         hacker worth his or her salt can quickly defeat all but the most paranoid
         security measures if he or she can gain physical access to a server. To pro-
         tect the server, follow these guidelines:

          ✦ Lock the computer room.
          ✦ Give the keys only to people you trust.
          ✦ Keep track of who has the keys.
          ✦ Mount the servers on cases or racks that have locks.
          ✦ Disable the floppy drive on the server. (A common hacking technique
            is to boot the server from a floppy, thus bypassing the carefully crafted
            security features of the network operating system.)
          ✦ Keep a trained guard dog in the computer room and feed it only enough
            to keep it hungry and mad. (Just kidding.)

         There’s a big difference between a locked door and a door with a lock. Locks
         are worthless if you don’t use them.

         Client computers should be physically secure as well. You should instruct
         users to not leave their computers unattended while they’re logged on. In
         high-traffic areas (such as the receptionist’s desk), users should secure
         their computers with the keylock. Additionally, users should lock their office
         doors when they leave.

         Here are some other potential threats to physical security that you may not
         have considered:

          ✦ The nightly cleaning crew probably has complete access to your facil-
            ity. How do you know that the person who vacuums your office every
            night doesn’t really work for your chief competitor or doesn’t consider
            computer hacking to be a sideline hobby? You don’t, so you’d better
            consider the cleaning crew a threat.
          ✦ What about your trash? Paper shredders aren’t just for Enron accoun-
            tants. Your trash can contain all sorts of useful information: sales
            reports, security logs, printed copies of the company’s security policy,
            even handwritten passwords. For the best security, every piece of paper
            that leaves your building via the trash bin should first go through a
            shredder.
          ✦ Where do you store your backup tapes? Don’t just stack them up next
            to the server. Not only does that make them easy to steal, it also defeats
            one of the main purposes of backing up your data in the first place:
            securing your server from physical threats, such as fires. If a fire burns
            down your computer room and the backup tapes are sitting unprotected
                                                Securing User Accounts         189

           next to the server, your company may go out of business — and you’ll
           certainly be out of a job. Store the backup tapes securely in a fireproof
           safe and keep a copy off-site, too.
        ✦ I’ve seen some networks in which the servers are in a locked computer
          room, but the hubs or switches are in an unsecured closet. Remember
          that every unused port on a hub or a switch represents an open door
          to your network. The hubs and switches should be secured just like the
          servers.



Securing User Accounts
       Next to physical security, the careful use of user accounts is the most impor-
       tant type of security for your network. Properly configured user accounts
       can prevent unauthorized users from accessing the network, even if they
       gain physical access to the network. The following sections describe some
       of the steps that you can take to strengthen your network’s use of user
       accounts.


       Obfuscating your usernames
       Huh? When it comes to security, obfuscation simply means picking obscure
       usernames. For example, most network administrators assign usernames              Book III
       based on some combination of the user’s first and last names, such as            Chapter 2
       BarnyM or baMiller. However, a hacker can easily guess such a user ID if he
       or she knows the name of at least one employee. After the hacker knows a
       username, he or she can focus on breaking the password.




                                                                                              Security 101
       You can slow down a hacker by using names that are more obscure. Here
       are some suggestions on how to do that:

        ✦ Add a random three-digit number to the end of the name. For example:
          BarnyM320 or baMiller977.
        ✦ Throw a number or two into the middle of the name. For example:
          Bar6nyM or ba9Miller2.
        ✦ Make sure that usernames are different from e-mail addresses. For exam-
          ple, if a user’s e-mail address is baMiller@Mydomain.com, do not use
          baMiller as the user’s account name. Use a more obscure name.

       Do not rely on obfuscation to keep people out of your network! Security by
       obfuscation doesn’t work. A resourceful hacker can discover even the most
       obscure names. The purpose of obfuscation is to slow intruders down — not
       to stop them. If you slow an intruder down, you’re more likely to discover
       that he or she is trying to crack your network before he or she successfully
       gets in.
190   Securing User Accounts


         Using passwords wisely
         One of the most important aspects of network security is the use of pass-
         words. Usernames aren’t usually considered secret. Even if you use obscure
         names, casual hackers will eventually figure them out.

         Passwords, on the other hand, are top secret. Your network password is the
         one thing that keeps an impostor from logging on to the network by using
         your username and therefore receiving the same access rights that you ordi-
         narily have. Guard your password with your life.

         Here are some tips for creating good passwords:

          ✦ Don’t use obvious passwords, such as your last name, your kid’s name,
            or your dog’s name.
          ✦ Don’t pick passwords based on your hobbies, either. A friend of mine
            is into boating, and his password is the name of his boat. Anyone who
            knows him can guess his password after a few tries. Five lashes for
            naming your password after your boat.
          ✦ Store your password in your head — not on paper. Especially bad:
            Writing down your password on a sticky note and sticking it on your
            computer’s monitor. Ten lashes for that. (If you must write down your
            password, write it on digestible paper that you can swallow after you’ve
            memorized the password.)
          ✦ Most network operating systems enable you to set an expiration time
            for passwords. For example, you can specify that passwords expire after
            30 days. When a user’s password expires, the user must change it. Your
            users may consider this process a hassle, but it helps to limit the risk
            of someone swiping a password and then trying to break into your com-
            puter system later.
          ✦ You can also configure user accounts so that when they change pass-
            words, they can’t specify a password that they’ve used recently. For
            example, you can specify that the new password can’t be identical to
            any of the user’s past three passwords.
          ✦ You can also configure security policies so that passwords must include
            a mixture of uppercase letters, lowercase letters, numerals, and special
            symbols. Thus, passwords like DIMWIT or DUFUS are out. Passwords like
            87dIM@wit or duF39&US are in.
          ✦ One of the newest trends is the use of devices that read fingerprints as a
            way to keep passwords. These devices store your passwords in a secret
            encoded file, then supply them automatically to whatever programs or
            Web sites require them — but only after the device has read your finger-
            print. Fingerprint readers used to be exotic and expensive, but you can
            now add a fingerprint reader to a computer for as little as $50.
                                           Securing User Accounts         191

A Password Generator For Dummies
How do you come up with passwords that no one can guess but that you
can remember? Most security experts say that the best passwords don’t cor-
respond to any words in the English language, but they consist of a random
sequence of letters, numbers, and special characters. Yet, how in the heck
are you supposed to memorize a password like Dks4%DJ2? Especially when
you have to change it three weeks later to something like 3pQ&X(d8.

Here’s a compromise solution that enables you to create passwords that
consist of two four-letter words back to back. Take your favorite book (if it’s
this one, you need to get a life) and turn to any page at random. Find the first
four- or five-letter word on the page. Suppose that word is When. Then repeat
the process to find another four- or five-letter word; say you pick the word
Most the second time. Now combine the words to make your password:
WhenMost. I think you agree that WhenMost is easier to remember than
3PQ&X(D8 and is probably just about as hard to guess. I probably wouldn’t
want the folks at the Los Alamos Nuclear Laboratory using this scheme, but
it’s good enough for most of us.

Here are some additional thoughts on concocting passwords from your
favorite book:

 ✦ If the words end up being the same, pick another word. And pick dif-               Book III
   ferent words if the combination seems too commonplace, such as                    Chapter 2
   WestWind or FootBall.
 ✦ For an interesting variation, insert the page numbers on which you




                                                                                           Security 101
   found both words either before or after the words. For example:
   135Into376Cat or 87Tree288Wing. The resulting password will be a
   little harder to remember, but you’ll have a password worthy of a Dan
   Brown novel.
 ✦ To further confuse your friends and enemies, use medieval passwords
   by picking words from Chaucer’s Canterbury Tales. Chaucer is a great
   source for passwords because he lived before the days of word proces-
   sors with spell-checkers. He wrote seyd instead of said, gret instead of
   great, and litel instead of little. And he used lots of seven-letter and eight-
   letter words suitable for passwords, such as glotenye (gluttony), benygne
   (benign), and opynyoun (opinion). And he got As in English.
 ✦ If you use any of these password schemes and someone breaks into
   your network, don’t blame me. You’re the one who’s too lazy to memo-
   rize D#Sc$h4@bb3xaz5.
 ✦ If you do decide to go with passwords such as KdI22UR3xdkL, you can
   find random password generators on the Internet. Just go to a search
   engine, such as Google (www.google.com), and search for password
   generator. You can find Web pages that generate random passwords
192   Hardening Your Network


             based on criteria that you specify, such as how long the password
             should be, whether it should include letters, numbers, punctuation,
             uppercase and lowercase letters, and so on.


         Securing the Administrator account
         It stands to reason that at least one network user must have the authority
         to use the network without any of the restrictions imposed on other users.
         This user is called the administrator. The administrator is responsible for set-
         ting up the network’s security system. To do that, the administrator must be
         exempt from all security restrictions.

         Many networks automatically create an administrator user account when
         you install the network software. The username and password for this ini-
         tial administrator are published in the network’s documentation and are
         the same for all networks that use the same network operating system. One
         of the first things that you must do after getting your network up and run-
         ning is to change the password for this standard administrator account.
         Otherwise, your elaborate security precautions will be a complete waste of
         time. Anyone who knows the default administrator username and password
         can access your system with full administrator rights and privileges, thus
         bypassing the security restrictions that you so carefully set up.

         Don’t forget the password for the administrator account! If a network user
         forgets his or her password, you can log on as the supervisor and change
         that user’s password. If you forget the administrator’s password, though,
         you’re stuck.



Hardening Your Network
         In addition to taking care of physical security and user account security, you
         should also take steps to protect your network from intruders by configuring
         the other security features of the network’s servers and routers. The follow-
         ing sections describe the basics of hardening your network.


         Using a firewall
         A firewall is a security-conscious router that sits between your network and
         the outside world and prevents Internet users from wandering into your LAN
         and messing around. Firewalls are the first line of defense for any network
         that’s connected to the Internet. You should never connect a network to the
         Internet without installing a carefully configured firewall. For more informa-
         tion about firewalls, refer to Chapter 4 of this book.
                                                    Securing Your Users       193

       Disabling unnecessary services
       A typical network operating system can support dozens of different types of
       network services: file and printer sharing, Web server, mail server, and many
       others. In many cases, these features are installed on servers that don’t need
       or use them. When a server runs a network service that it doesn’t really
       need, the service not only robs CPU cycles from other services that are
       needed, but also poses an unnecessary security threat.

       When you first install a network operating system on a server, you should
       enable only those network services that you know the server will require.
       You can always enable services later if the needs of the server change.


       Patching your servers
       Hackers regularly find security holes in network operating systems. After
       those holes are discovered, the operating system vendors figure out how
       to plug the hole and release a software patch for the security fix. The trou-
       ble is that most network administrators don’t stay up to date with these
       software patches. As a result, many networks are vulnerable because they
       have well-known holes in their security armor that should have been fixed
       but weren’t.

       Even though patches are a bit of a nuisance, they’re well worth the effort        Book III
       for the protection that they afford. Fortunately, newer versions of the popu-    Chapter 2
       lar network operating systems have features that automatically check for
       updates and let you know when a patch should be applied.




                                                                                              Security 101
Securing Your Users
       Security techniques, such as physical security, user account security, server
       security, and locking down your servers, are child’s play compared to the
       most difficult job of network security: securing your network’s users. All
       the best-laid security plans will go for naught if your users write down their
       passwords on sticky notes and post them on their computers.

       The key to securing your network users is to create a written network security
       policy and stick to it. Have a meeting with everyone to go over the security
       policy to make sure that everyone understands the rules. Also, make sure to
       have consequences when violations occur.

       Here are some suggestions for some basic security rules you can incorpo-
       rate into your security policy:
194   Securing Your Users


          ✦ Never write down your password or give it to someone else.
          ✦ Accounts should not be shared. Never use someone else’s account to
            access a resource that you can’t access under your own account. If you
            need access to some network resource that isn’t available to you, you
            should formally request access under your own account.
          ✦ Likewise, never give your account information to a coworker so that he
            or she can access a needed resource. Your coworker should instead for-
            mally request access under his or her own account.
          ✦ Don’t install any software or hardware on your computer — especially
            wireless access devices or modems — without first obtaining permission.
          ✦ Don’t enable file and printer sharing on workstations without first get-
            ting permission.
          ✦ Never attempt to disable or bypass the network’s security features.
       Chapter 3: Managing
       User Accounts
       In This Chapter
       ✓ Understanding user accounts
       ✓ Looking at the built-in accounts
       ✓ Using rights and permissions
       ✓ Working with groups and policies
       ✓ Running login scripts




       U      ser accounts are the backbone of network security administration.
              Through the use of user accounts, you can determine who can access
       your network, as well as what network resources each user can and can’t
       access. You can restrict access to the network to just specific computers
       or to certain hours of the day. In addition, you can lock out users who no
       longer need to access your network.

       The specific details for managing user accounts are unique to each network
       operating system and are covered in separate chapters later in this book.
       The purpose of this chapter is simply to introduce you to the concepts of
       user account management, so you know what you can and can’t do, regard-
       less of which network operating system you use.



Exploring What User Accounts Consist Of
       Every user who accesses a network must have a user account. User accounts
       allow the network administrator to determine who can access the network
       and what network resources each user can access. In addition, the user
       account can be customized to provide many convenience features for users,
       such as a personalized Start menu or a display of recently used documents.

       Every user account is associated with a username (sometimes called a
       user ID), which the user must enter when logging on to the network. Each
       account also has other information associated with it. In particular:

        ✦ The user’s password: This also includes the password policy, such as
          how often the user has to change his or her password, how complicated
          the password must be, and so on.
196   Looking at Built-In Accounts


          ✦ The user’s contact information: This includes full name, phone number,
            e-mail address, mailing address, and other related information.
          ✦ Account restrictions: This includes restrictions that allow the user to
            log on only during certain times of the day. This feature enables you to
            restrict your users to normal working hours so that they can’t sneak in
            at 2 a.m. to do unauthorized work. This feature also discourages your
            users from working overtime because they can’t access the network
            after hours, so use it judiciously. You can also specify that the user can
            log on only at certain computers.
          ✦ Account status: You can temporarily disable a user account so that the
            user can’t log on.
          ✦ Home directory: This specifies a shared network folder where the user
            can store documents.
          ✦ Dial-in permissions: These authorize the user to access the network
            remotely via a dialup connection.
          ✦ Group memberships: These grant the user certain rights based on
            groups to which they belong. For more information, see the section,
            “Assigning Permissions to Groups,” later in this chapter.



Looking at Built-In Accounts
         Most network operating systems come preconfigured with two built-in
         accounts, named Administrator and Guest. In addition, some server services,
         such as Web or database servers, create their own user accounts under
         which to run. The following sections describe the characteristics of these
         accounts.


         The Administrator account
         The Administrator account is the King of the Network. This user account
         isn’t subject to any of the account restrictions to which other, mere mortal
         accounts must succumb. If you log on as the administrator, you can do
         anything.

         Because the Administrator account has unlimited access to your network,
         it’s imperative that you secure it immediately after you install the server.
         When the NOS Setup program asks for a password for the Administrator
         account, start off with a good random mix of uppercase and lowercase let-
         ters, numbers, and symbols. Don’t pick some easy-to-remember password to
         get started, thinking you’ll change it to something more cryptic later. You’ll
         forget, and in the meantime, someone will break in and reformat the server’s
         C: drive or steal your customers’ credit card numbers.
                                   Looking at Built-In Accounts       197

Here are a few additional things worth knowing about the Administrator
account:

 ✦ You can’t delete it. The system must always have an administrator.
 ✦ You can grant administrator status to other user accounts. However,
   you should do so only for users who really need to be administrators.
 ✦ You should use it only when you really need to do tasks that require
   administrative authority. Many network administrators grant adminis-
   trative authority to their own user accounts. That isn’t a very good idea.
   If you’re killing some time surfing the Web or reading your e-mail while
   logged on as an administrator, you’re just inviting viruses or malicious
   scripts to take advantage of your administrator access. Instead, you
   should set yourself up with two accounts: a normal account that you
   use for day-to-day work, and an Administrator account that you use only
   when you need it.
 ✦ The default name for the Administrator account is usually simply
   Administrator. You may want to consider changing this name. Better
   yet, change the name of the Administrator account to something more
   obscure and then create an ordinary user account that has few — if
   any — rights and give that account the name Administrator. That way,
   hackers who spend weeks trying to crack your Administrator account
   password will discover that they’ve been duped, once they finally break       Book III
   the password. In the meantime, you’ll have a chance to discover their        Chapter 3
   attempts to breach your security and take appropriate action.
 ✦ Above all, don’t forget the Administrator account password. Write it




                                                                                   Managing User
   down in permanent ink and store it in Fort Knox, a safe-deposit box, or




                                                                                     Accounts
   some other secure location.

The Guest account
Another commonly created default account is called the Guest account. This
account is set up with a blank password and few — if any — access rights.
The Guest account is designed to allow people to step up to a computer and
log on, but after they do, it then prevents them from doing anything. Sounds
like a waste of time to me. I suggest you disable the Guest account.


Service accounts
Some network users aren’t actual people. I don’t mean that some of your
users are subhuman. Rather, some users are actually software processors
that require access to secure resources and therefore require user accounts.
These user accounts are usually created automatically for you when you
install or configure server software.
198   Assigning Using Rights


         For example, when you install Microsoft’s Web server (IIS), an Internet
         user account called IUSR is created. The complete name for this account is
         IUSR_<servername>. So if the server is named WEB1, the account is named
         IUSR_WEB1. IIS uses this account to allow anonymous Internet users to
         access the files of your Web site.

         As a general rule, you shouldn’t mess with these accounts unless you know
         what you’re doing. For example, if you delete or rename the IUSR account,
         you must reconfigure IIS to use the changed account. If you don’t, IIS will
         deny access to anyone trying to reach your site. (Assuming that you do
         know what you’re doing, renaming these accounts can increase your net-
         work’s security. However, don’t start playing with these accounts until
         you’ve researched the ramifications.)



Assigning User Rights
         User accounts and passwords are only the front line of defense in the game
         of network security. After a user gains access to the network by typing a
         valid user ID and password, the second line of security defense — rights —
         comes into play.

         In the harsh realities of network life, all users are created equal, but some
         users are more equal than others. The Preamble to the Declaration of
         Network Independence contains the statement, “We hold these truths to be
         self-evident, that some users are endowed by the network administrator with
         certain inalienable rights. . . .”

         The specific rights that you can assign to network users depend on which
         network operating system you use. Here’s a partial list of the user rights that
         are possible with Windows servers:

          ✦ Log on locally: The user can log on to the server computer directly from
            the server’s keyboard.
          ✦ Change system time: The user can change the time and date registered
            by the server.
          ✦ Shut down the system: The user can perform an orderly shutdown of
            the server.
          ✦ Back up files and directories: The user can perform a backup of files
            and directories on the server.
          ✦ Restore files and directories: The user can restore backed-up files.
          ✦ Take ownership of files and other objects: The user can take over files
            and other network resources that belong to other users.
       Controlling User Access with Permissions (Who Gets What)                        199

Controlling User Access with Permissions
(Who Gets What)
       User rights control what a user can do on a network-wide basis. Permissions
       enable you to fine-tune your network security by controlling access to
       specific network resources, such as files or printers, for individual users
       or groups. For example, you can set up permissions to allow users in the
       accounting department to access files in the server’s \ACCTG directory.
       Permissions can also enable some users to read certain files but not modify
       or delete them.

       Each network operating system manages permissions in a different way.
       Whatever the details, the effect is that you can give permission to each user
       to access certain files, folders, or drives in certain ways.

       Any permissions that you specify for a folder apply automatically to any of
       that folder’s subfolders, unless you explicitly specify a different set of per-
       missions for the subfolder.

       Windows refers to file system rights as permissions. Windows servers have
       six basic permissions, listed in Table 3-1. You can assign any combination of
       Windows permissions to a user or group for a given file or folder.
                                                                                              Book III
                                                                                             Chapter 3

         Table 3-1                    Windows Basic Permissions




                                                                                                Managing User
                                                                                                  Accounts
         Permission           Abbreviation      What the User Can Do
         Read                 R                 The user can open and read the file.
         Write                W                 The user can open and write to the file.
         Execute              X                 The user can run the file.
         Delete               D                 The user can delete the file.
         Change               P                 The user can change the permissions for
                                                the file.
         Take Ownership       O                 The user can take ownership of the file.


       Note the last permission listed in Table 3-1. In Windows, the concept of file
       or folder ownership is important. Every file or folder on a Windows server
       system has an owner. The owner is usually the user who creates the file or
       folder. However, ownership can be transferred from one user to another. So
       why the Take Ownership permission? This permission prevents someone
       from creating a bogus file and giving ownership of it to you without your
200   Assigning Permissions to Groups


         permission. Windows doesn’t allow you to give ownership of a file to another
         user. Instead, you can give another user the right to take ownership of the
         file. That user must then explicitly take ownership of the file.

         You can use Windows permissions only for files or folders that are created
         on drives formatted as NTFS volumes. If you insist on using FAT or FAT32 for
         your Windows shared drives, you can’t protect individual files or folders on
         the drives. This is one of the main reasons for using NTFS for your Windows
         servers.



Assigning Permissions to Groups
         A group account is an account that doesn’t represent an individual user.
         Instead, it represents a group of users who use the network in a similar way.
         Instead of granting access rights to each of these users individually, you can
         grant the rights to the group and then assign individual users to the group.
         When you assign a user to a group, that user inherits the rights specified for
         the group.

         For example, suppose that you create a group named Accounting for the
         accounting staff and then allow members of the Accounting group access
         to the network’s accounting files and applications. Then, instead of grant-
         ing each accounting user access to those files and applications, you simply
         make each accounting user a member of the Accounting group.

         Here are a few additional details about groups:

          ✦ Groups are key to network-management nirvana. As much as pos-
            sible, you should avoid managing network users individually. Instead,
            clump them into groups and manage the groups. When all 50 users in
            the accounting department need access to a new file share, would you
            rather update 50 user accounts or just one group account?
          ✦ A user can belong to more than one group. Then, the user inherits the
            rights of each group. For example, suppose that you have groups set
            up for Accounting, Sales, Marketing, and Finance. A user who needs to
            access both Accounting and Finance information can be made a member
            of both the Accounting and Finance groups. Likewise, a user who needs
            access to both Sales and Marketing information can be made a member
            of both the Sales and Marketing groups.
          ✦ You can grant or revoke specific rights to individual users to override
            the group settings. For example, you may grant a few extra permissions
            for the manager of the Accounting department. You may also impose a
            few extra restrictions on certain users.
                                Automating Tasks with Logon Scripts          201

Understanding User Profiles
       A user profile is a Windows feature that keeps track of an individual user’s
       preferences for his or her Windows configuration. For a non-networked com-
       puter, profiles enable two or more users to use the same computer, each
       with his or her own desktop settings, such as wallpaper, colors, Start menu
       options, and so on.

       The real benefit of user profiles becomes apparent when profiles are used on
       a network. A user’s profile can be stored on a server computer and accessed
       whenever that user logs on to the network from any Windows computer on
       the network.

       The following are some of the elements of Windows that are governed by
       settings in the user profile:

        ✦ Desktop settings from the Display Properties dialog box, including wall-
          paper, screen savers, and color schemes
        ✦ Start menu programs and Windows toolbar options
        ✦ Favorites, which provide easy access to the files and folders that the
          user accesses frequently
        ✦ Network settings, including drive mappings, network printers, and            Book III
          recently visited network locations                                          Chapter 3

        ✦ Application settings, such as option settings for Microsoft Word




                                                                                         Managing User
        ✦ The Documents folder (My Documents in Windows XP)




                                                                                           Accounts
Automating Tasks with Logon Scripts
       A logon script is a batch file that runs automatically whenever a user logs
       on. Logon scripts can perform several important logon tasks for you, such
       as mapping network drives, starting applications, synchronizing the client
       computer’s time-of-day clock, and so on. Logon scripts reside on the server.
       Each user account can specify whether to use a logon script and which
       script to use.

       Here’s a sample logon script that maps a few network drives and synchro-
       nizes the time:

       net   use m: \\MYSERVER\Acct
       net   use n: \\MYSERVER\Admin
       net   use o: \\MYSERVER\Dev
       net   time \\MYSERVER /set /yes
202   Automating Tasks with Logon Scripts


         Logon scripts are a little out of vogue because most of what a logon script
         does can be done via user profiles. Still, many administrators prefer the sim-
         plicity of logon scripts, so they’re still used even on Windows Server 2003
         and 2008 systems.
       Chapter 4: Firewalls and
       Virus Protection
       In This Chapter
       ✓ Understanding what firewalls do
       ✓ Examining the different types of firewalls
       ✓ Looking at virus protection
       ✓ Discovering Windows security




       I  f your network is connected to the Internet, a whole host of security
          issues bubble to the surface. You probably connected your network
       to the Internet so that your network’s users could access the Internet.
       Unfortunately, however, your Internet connection is a two-way street. Not
       only does it enable your network’s users to step outside the bounds of your
       network to access the Internet, but it also enables others to step in and
       access your network.

       And step in they will. The world is filled with hackers looking for networks
       like yours to break into. They may do it just for fun, or they may do it to
       steal your customer’s credit card numbers or to coerce your mail server
       into sending thousands of spam messages on their behalf. Whatever their
       motive, rest assured that your network will be broken into if you leave it
       unprotected.

       This chapter presents an overview of two basic techniques for securing
       your network’s Internet connection: firewalls and virus protection.



Firewalls
       A firewall is a security-conscious router that sits between the Internet and
       your network with a single-minded task: preventing them from getting to us.
       The firewall acts as a security guard between the Internet and your local
       area network (LAN). All network traffic into and out of the LAN must pass
       through the firewall, which prevents unauthorized access to the network.
204      Firewalls


              Some type of firewall is a must-have if your network has a connection to the
              Internet, whether that connection is broadband (cable modem or digital sub-
              scriber line; DSL), T1, or some other high-speed connection. Without it,
              sooner or later a hacker will discover your unprotected network and tell his
              friends about it. Within a few hours, your network will be toast.

              You can set up a firewall two basic ways. The easiest way is to purchase a
              firewall appliance, which is basically a self-contained router with built-in
              firewall features. Most firewall appliances include a Web-based interface
              that enables you to connect to the firewall from any computer on your net-
              work using a browser. You can then customize the firewall settings to suit
              your needs.

              Alternatively, you can set up a server computer to function as a firewall
              computer. The server can run just about any network operating system, but
              most dedicated firewall systems run Linux.

              Whether you use a firewall appliance or a firewall computer, the firewall
              must be located between your network and the Internet, as shown in Figure
              4-1. Here, one end of the firewall is connected to a network hub, which is in
              turn connected to the other computers on the network. The other end of the
              firewall is connected to the Internet. As a result, all traffic from the LAN to
              the Internet and vice versa must travel through the firewall.




                                        Switch


Figure 4-1:                                                 The Internet
Using a
firewall
                                    Firewall Router
appliance.
                                              The Many Types of Firewalls         205

       The term perimeter is sometimes used to describe the location of a firewall on
       your network. In short, a firewall is like a perimeter fence that completely sur-
       rounds your property and forces all visitors to enter through the front gate.



The Many Types of Firewalls
       Firewalls employ four basic techniques to keep unwelcome visitors out of
       your network. The following sections describe these basic firewall techniques.


       Packet filtering
       A packet-filtering firewall examines each packet that crosses the firewall and
       tests the packet according to a set of rules that you set up. If the packet
       passes the test, it’s allowed to pass. If the packet doesn’t pass, it’s rejected.

       Packet filters are the least expensive type of firewall. As a result, packet-
       filtering firewalls are very common. However, packet filtering has a number
       of flaws that knowledgeable hackers can exploit. As a result, packet filtering
       by itself doesn’t make for a fully effective firewall.

       Packet filters work by inspecting the source and destination IP and port
       addresses contained in each Transmission Control Protocol/Internet Protocol
                                                                                             Book III
       (TCP/IP) packet. TCP/IP ports are numbers that are assigned to specific ser-
                                                                                            Chapter 4
       vices that help to identify for which service each packet is intended. For exam-
       ple, the port number for the HTTP protocol is 80. As a result, any incoming




                                                                                               Virus Protection
       packets headed for an HTTP server will specify port 80 as the destination port.




                                                                                                Firewalls and
       Port numbers are often specified with a colon following an IP address. For
       example, the HTTP service on a server whose IP address is 192.168.10.133
       would be 192.168.10.133:80.

       Literally thousands of established ports are in use. Table 4-1 lists a few of
       the most popular ports.



         Table 4-1                    Some Well-Known TCP/IP Ports
         Port           Description
         20             File Transfer Protocol (FTP)
         21             File Transfer Protocol (FTP)
         22             Secure Shell Protocol (SSH)
         23             Telnet
         25             Simple Mail Transfer Protocol (SMTP)
                                                                              (continued)
206   The Many Types of Firewalls



           Table 4-1 (continued)
           Port           Description
           53             Domain Name Server (DNS)
           80             World Wide Web (HyperText Transport Protocol; HTTP)
           110            Post Office Protocol (POP3)
           119            Network News Transfer Protocol (NNTP)
           137            NetBIOS Name Service
           138            NetBIOS Datagram Service
           139            NetBIOS Session Service
           143            Internet Message Access Protocol (IMAP)
           161            Simple Network Management Protocol (SNMP)
           194            Internet Relay Chat (IRC)
           389            Lightweight Directory Access Protocol (LDAP)
           396            NetWare over IP
           443            HTTP over TLS/SSL (HTTPS)


         The rules that you set up for the packet filter either permit or deny packets
         that specify certain IP addresses or ports. For example, you may permit
         packets that are intended for your mail server or your Web server and deny
         all other packets. Or, you may set up a rule that specifically denies packets
         that are heading for the ports used by NetBIOS. This rule keeps Internet
         hackers from trying to access NetBIOS server resources, such as files or
         printers.

         One of the biggest weaknesses of packet filtering is that it pretty much trusts
         that the packets themselves are telling the truth when they say who they’re
         from and who they’re going to. Hackers exploit this weakness by using a
         hacking technique called IP spoofing, in which they insert fake IP addresses
         in packets that they send to your network.

         Another weakness of packet filtering is that it examines each packet in
         isolation without considering what packets have gone through the firewall
         before and what packets may follow. In other words, packet filtering is state-
         less. Rest assured that hackers have figured out how to exploit the stateless
         nature of packet filtering to get through firewalls.
                                    The Many Types of Firewalls          207

In spite of these weaknesses, packet filter firewalls have several advantages
that explain why they are commonly used:

 ✦ Packet filters are very efficient. They hold up each inbound and out-
   bound packet for only a few milliseconds while they look inside the
   packet to determine the destination and source ports and addresses.
   After these addresses and ports are determined, the packet filter quickly
   applies its rules and either sends the packet along or rejects it. In con-
   trast, other firewall techniques have a more noticeable performance
   overhead.
 ✦ Packet filters are almost completely transparent to users. The only
   time a user will be aware that a packet filter firewall is being used is
   when the firewall rejects packets. Other firewall techniques require that
   clients and/or servers be specially configured to work with the firewall.
 ✦ Packet filters are inexpensive. Most routers include built-in packet
   filtering.


Stateful packet inspection (SPI)
Stateful packet inspection, also known as SPI, is a step up in intelligence from
simple packet filtering. A firewall with stateful packet inspection looks at
packets in groups rather than individually. It keeps track of which packets
have passed through the firewall and can detect patterns that indicate unau-        Book III
thorized access. In some cases, the firewall may hold on to packets as they        Chapter 4
arrive until the firewall gathers enough information to make a decision about
whether the packets should be authorized or rejected.




                                                                                      Virus Protection
                                                                                       Firewalls and
Stateful packet inspection was once found only on expensive, enterprise-
level routers. Now, however, SPI firewalls are affordable enough for small- or
medium-sized networks to use.


Circuit-level gateway
A circuit-level gateway manages connections between clients and servers
based on TCP/IP addresses and port numbers. After the connection is
established, the gateway doesn’t interfere with packets flowing between
the systems.

For example, you could use a Telnet circuit-level gateway to allow Telnet
connections (port 23) to a particular server and prohibit other types of con-
nections to that server. After the connection is established, the circuit-level
gateway allows packets to flow freely over the connection. As a result, the
circuit-level gateway can’t prevent a Telnet user from running specific pro-
grams or using specific commands.
208   The Built-In Windows Firewall


         Application gateway
         An application gateway is a firewall system that is more intelligent than a
         packet-filtering firewall, stateful packet inspection, or circuit-level gateway
         firewall. Packet filters treat all TCP/IP packets the same. In contrast, appli-
         cation gateways know the details about the applications that generate the
         packets that pass through the firewall. For example, a Web application
         gateway is aware of the details of HTTP packets. As a result, it can examine
         more than just the source and destination addresses and ports to determine
         whether the packets should be allowed to pass through the firewall.

         In addition, application gateways work as proxy servers. Simply put, a proxy
         server is a server that sits between a client computer and a real server. The
         proxy server intercepts packets that are intended for the real server and pro-
         cesses them. The proxy server can examine the packet and decide to pass it
         on to the real server, or it can reject the packet. Or, the proxy server may be
         able to respond to the packet itself without involving the real server at all.

         For example, Web proxies often store copies of commonly used Web pages in
         a local cache. When a user requests a Web page from a remote Web server,
         the proxy server intercepts the request and checks whether it already has a
         copy of the page in its cache. If so, the Web proxy returns the page directly to
         the user. If not, the proxy passes the request on to the real server.

         Application gateways are aware of the details of how various types of TCP/
         IP servers handle sequences of TCP/IP packets to can make more intelligent
         decisions about whether an incoming packet is legitimate or is part of an
         attack. As a result, application gateways are more secure than simple packet-
         filtering firewalls, which can deal with only one packet at a time.

         The improved security of application gateways, however, comes at a price.
         Application gateways are more expensive than packet filters, both in terms
         of their purchase price and in the cost of configuring and maintaining them.
         In addition, application gateways slow network performance because they
         do more detailed checking of packets before allowing them to pass.



The Built-In Windows Firewall
         Windows comes with a built-in packet-filtering firewall. If you don’t have a
         separate firewall router, you can use this built-in firewall to provide a basic
         level of protection. Here are the steps to activate this feature in Windows 7:

          1. Choose Start➪Control Panel.
             Control Panel appears.
                                               The Built-In Windows Firewall         209

              2. Click System and Security.
                  The System and Security page appears.
              3. Click Windows Firewall.
                  The Windows Firewall page appears.
              4. Click Turn Windows Firewall On or Off.
                  The page shown in Figure 4-2 appears.




Figure 4-2:
Activating
                                                                                                Book III
the fire-                                                                                      Chapter 4
wall in
Windows 7.




                                                                                                  Virus Protection
                                                                                                   Firewalls and
              5. Click Turn On Windows Firewall.
              6. Click OK.
                  The firewall is enabled.

              Do not enable Windows Firewall if you’re using a separate firewall router to
              protect your network. Because the other computers on the network are con-
              nected directly to the router and not to your computer, Windows Firewall
              won’t protect the rest of the network. Additionally, as an unwanted side
              effect, the rest of the network will lose the ability to access your computer.

              Windows Firewall is turned on by default. If your computer is already
              behind a firewall, you should disable Windows Firewall. (In some cases, the
              network’s group policy settings may prevent you from disabling Windows
              Firewall. In that case, you must change the group policy so that Windows
              Firewall can be disabled. For more information about group policy, see Book
              VII, Chapter 6.)
210   Virus Protection


Virus Protection
         Viruses are one of the most misunderstood computer phenomena around
         these days. What is a virus? How does it work? How does it spread from
         computer to computer? I’m glad you asked.


         What is a virus?
         Make no mistake — viruses are real. Now that most people are connected
         to the Internet, viruses have really taken off. Every computer user is suscep-
         tible to attacks by computer viruses, and using a network increases your vul-
         nerability because it exposes all network users to the risk of being infected
         by a virus that lands on any one network user’s computer.

         Viruses don’t just spontaneously appear out of nowhere. Viruses are com-
         puter programs that are created by malicious programmers who’ve lost a
         few screws and should be locked up.

         What makes a virus a virus is its capability to make copies of itself that can
         be spread to other computers. These copies, in turn, make still more copies
         that spread to still more computers, and so on, ad nauseam.

         Then, the virus patiently waits until something triggers it — perhaps when
         you type a particular command or press a certain key, when a certain date
         arrives, or when the virus creator sends the virus a message. What the virus
         does when it strikes also depends on what the virus creator wants the virus
         to do. Some viruses harmlessly display a “gotcha” message. Some send an
         e-mail to everyone it finds in your address book. Some wipe out all the data
         on your hard drive. Ouch.

         A few years back, viruses moved from one computer to another by latching
         themselves onto floppy disks. Whenever you borrowed a floppy disk from
         a buddy, you ran the risk of infecting your own computer with a virus that
         may have stowed away on the disk.

         Virus programmers have discovered that e-mail is a very efficient method
         to spread their viruses. Typically, a virus masquerades as a useful or inter-
         esting e-mail attachment, such as instructions on how to make $1,000,000
         in your spare time, pictures of naked celebrities, or a Valentine’s Day greet-
         ing from your long-lost sweetheart. When a curious but unsuspecting user
         double-clicks the attachment, the virus springs to life, copying itself onto
         the user’s computer — and, in some cases, sending copies of itself to all the
         names in the user’s address book.

         After the virus works its way onto a networked computer, the virus can then
         figure out how to spread itself to other computers on the network.
                                                   Virus Protection      211

Here are some more tidbits about protecting your network from virus
attacks:

 ✦ The term virus is often used to refer not only to true virus programs
   (which are able to replicate themselves) but also to any other type
   of program that’s designed to harm your computer. These programs
   include so-called Trojan horse programs that usually look like games but
   are, in reality, hard drive formatters.
 ✦ A worm is similar to a virus, but it doesn’t actually infect other files.
   Instead, it just copies itself onto other computers on a network. After
   a worm has copied itself onto your computer, there’s no telling what it
   may do there. For example, a worm may scan your hard drive for inter-
   esting information, such as passwords or credit card numbers, and then
   e-mail them to the worm’s author.
 ✦ Computer virus experts have identified several thousand “strains” of
   viruses. Many of them have colorful names, such as the I Love You virus,
   the Stoned virus, and the Michelangelo virus.
 ✦ Antivirus programs can recognize known viruses and remove them from
   your system, and they can spot the telltale signs of unknown viruses.
   Unfortunately, the idiots who write viruses aren’t idiots (in the intellectual
   sense), so they’re constantly developing new techniques to evade detec-
   tion by antivirus programs. New viruses are frequently discovered, and            Book III
   antivirus programs are periodically updated to detect and remove them.           Chapter 4


Antivirus programs




                                                                                       Virus Protection
                                                                                        Firewalls and
The best way to protect your network from virus infection is to use an
antivirus program. These programs have a catalog of several thousand
known viruses that they can detect and remove. In addition, they can spot
the types of changes that viruses typically make to your computer’s files,
thus decreasing the likelihood that some previously unknown virus will go
undetected.

It would be nice if Windows came with built-in antivirus software, but alas —
it does not. You have to purchase a program on your own. The two best-
known antivirus programs for Windows are Norton AntiVirus by Symantec
and VirusScan by McAfee.

The people who make antivirus programs have their fingers on the pulse of
the virus world and frequently release updates to their software to combat the
latest viruses. Because virus writers are constantly developing new viruses,
your antivirus software is next to worthless unless you keep it up to date by
downloading the latest updates.
212   Virus Protection


         Here are several approaches to deploying antivirus protection on your
         network:

          ✦ Install antivirus software on each network user’s computer. This tech-
            nique would be the most effective if you could count on all your users
            to keep their antivirus software up to date. Because that’s an unlikely
            proposition, you may want to adopt a more reliable approach to virus
            protection.
          ✦ Managed antivirus services place antivirus client software on each
            client computer in your network. Then, an antivirus server automati-
            cally updates the clients on a regular basis to make sure that they’re
            kept up to date.
          ✦ Server-based antivirus software protects your network servers from
            viruses. For example, you can install antivirus software on your mail
            server to scan all incoming mail for viruses and remove them before
            your network users ever see them.
          ✦ Some firewall appliances include antivirus enforcement checks that
            don’t allow your users to access the Internet unless their antivirus
            software is up to date. This type of firewall provides the best antivirus
            protection available.


         Safe computing
         Besides using an antivirus program, you can take a few additional precau-
         tions to ensure virus-free computing. If you haven’t talked to your kids about
         these safe-computing practices, you had better do so soon.

          ✦ Regularly back up your data. If a virus hits you, and your antivirus soft-
            ware can’t repair the damage, you may need the backup to recover your
            data. Make sure that you restore from a backup that was created before
            you were infected by the virus!
          ✦ If you buy software from a store and discover that the seal has been
            broken on the disk package, take the software back. Don’t try to install
            it on your computer. You don’t hear about tainted software as often as
            you hear about tainted beef, but if you buy software that’s been opened,
            it may well be laced with a virus infection.
          ✦ Use your antivirus software to scan your disk for virus infection after
            your computer has been to a repair shop or worked on by a consultant.
            These guys don’t intend harm, but they occasionally spread viruses acci-
            dentally, simply because they work on so many strange computers.
          ✦ Don’t open e-mail attachments from people you don’t know or attach-
            ments you weren’t expecting.
          ✦ Use your antivirus software to scan any floppy disk or CD that doesn’t
            belong to you before you access any of its files.
                                               Using Windows Action Center         213

Using Windows Action Center
              Windows 7 includes a new feature called the Windows Action Center. As
              shown in Figure 4-3, the Windows Action Center monitors the status of secu-
              rity-related issues on your computer. You can summon the Windows Action
              Center by opening the Control Panel, clicking System and Security, and then
              clicking Action Center.




Figure 4-3:                                                                                   Book III
The                                                                                          Chapter 4
Windows 7
Action




                                                                                                Virus Protection
                                                                                                 Firewalls and
Center.



              The Windows Action Center alerts you to issues with your computer’s secu-
              rity status as well as reminds you of maintenance that should be done, such
              as installing operating system updates.

              Here are a couple of additional points to ponder concerning the Windows
              Action Center:

               ✦ A flag icon (shown in the margin) appears in the notification area on the
                 right end of the Windows taskbar to alert you to items you should attend
                 to in the Windows Action Center.
               ✦ Windows Vista and Windows XP included a similar feature called the
                 Windows Security Center, which you can access from the Control Panel.
214   Book III: Network Administration and Security
      Chapter 5: Extending Your
      Network with VPN Access
      In This Chapter
      ✓ Examining the uses of VPN
      ✓ Looking at how VPN works
      ✓ Considering VPN clients and servers
      ✓ Pondering VPN hardware and software




      T   oday’s network users frequently need to access their networks from
          remote locations such as their home offices, hotel rooms, beach villas,
      and their kid’s soccer fields. In the early days of computer networking, the
      only real option for remotely accessing a network was to set up dial-up
      access with telephone lines and modems.

      Dial-up access worked, but it was slow and unreliable. Today, enabling
      remote access to a local area network is easily done with a virtual private
      network, or VPN. Simply put, VPN enables remote users to access a local
      area network via any Internet connection.

      This chapter is a short introduction to VPNs. You find out the basics of what
      a VPN is, how to set one up, and how to access one remotely. Enjoy!



Understanding VPN
      A virtual private network (VPN) is a type of network connection that creates
      the illusion that you’re directly connected to a network when in fact you are
      not. For example, suppose you’ve set up a local area network at your office
      but you also occasionally work from home. But how will you access the files
      on your work computer from home?

       ✦ You could simply copy whatever files you need from your work com-
         puter onto a flash drive and take them home with you, work on the files,
         copy the updated files back to the flash drive, and take them back to
         work with you the next day.
       ✦ You could e-mail the files to your personal e-mail account, work on
         them at home, and then e-mail the changed files back to your work
         e-mail account.
216   Looking at VPN Security


          ✦ You could get a laptop and use the Windows Offline Files feature to
            automatically synchronize files from your work network with files on the
            laptop.

         Or, you could set up a VPN that allows you to log on to your work network
         from home. The VPN uses a secured Internet connection to connect you
         directly to your work network, so you can access your network files as if you
         had a really long Ethernet cable that ran from your home computer all the
         way to the office and plugged directly into the work network.

         There are at least three situations in which a VPN is the ideal solution:

          ✦ One or more workers need to occasionally work from home (as in the
            scenario described above). In this situation, a VPN connection estab-
            lishes a connection between the home computer and the office network.
          ✦ One or more mobile users — who may not ever actually show up at the
            office — need to connect to the work network from mobile computers,
            often from locations like hotel rooms, clients’ offices, airports, or coffee
            shops. This type of VPN configuration is similar to the home user’s con-
            figuration, except that the exact location of the remote user’s computer
            is not fixed.
          ✦ Your company has offices in two or more locations, each with its own
            local area network, and you want to connect the locations so that users
            on either network can access each other’s network resources. In this
            situation, the VPN doesn’t connect a single user with a remote network;
            instead, it connects two remote networks to each other.



Looking at VPN Security
         The V in VPN stands for virtual, which means that a VPN creates the
         appearance of a local network connection when in fact the connection is
         made over a public network — the Internet. The term tunnel is sometimes
         used to describe a VPN because the VPN creates a tunnel between two
         locations which can only be entered from either end. The data that trav-
         els through the tunnel from one end to the other is secure as long as it is
         within the tunnel — that is, within the protection provided by the VPN.

         The P in VPN stands for private, which is the purpose of creating the tunnel.
         If the VPN did not create effective security so that data can enter the tunnel
         only at one of the two ends, the VPN would be worthless; you may as well
         just open your network and your remote computer up to the Internet and let
         the hackers have their way.

         Prior to VPN technology, the only way to provide private remote network
         connections was through actual private lines, which were (and still are) very
         expensive. For example, to set up a remote office you could lease a private
                               Understanding VPN Servers and Clients            217

       T1 line from the phone company to connect the two offices. This private T1
       line provided excellent security because it physically connected the two
       offices and could be accessed only from the two endpoints.

       VPN provides the same point-to-point connection as a private leased line,
       but does it over the Internet instead of through expensive dedicated lines.
       To create the tunnel that guarantees privacy of the data as it travels from
       one end of the VPN to the other, the data is encrypted using special security
       protocols.

       The most important of the VPN security protocols is called IPSec, which
       stands for Internet Protocol Security. IPSec is a collection of standards for
       encrypting and authenticating packets that travel on the Internet. In other
       words, it provides a way to encrypt the contents of a data packet so that only
       a person who knows the secret encryption keys can decode the data. And it
       provides a way to reliably identify the source of a packet so that the parties
       at either end of the VPN tunnel can trust that the packets are authentic.

       Referring to the OSI reference model presented in Chapter 2 of Book 1, the
       IPSec protocol operates at layer 3 of the OSI model, also called the Network
       layer. What that means is that the IPSec protocol has no idea about what
       kind of data is being carried by the packets it encrypts and authenticates.
       The IPSec protocol concerns itself only with the details of encrypting the
       contents of the packets (sometimes called the payload) and ensuring the             Book III
       identity of the sender.                                                            Chapter 5


       Another commonly used VPN protocol is L2TP. L2TP stands for Layer 2




                                                                                          Extending Your
                                                                                           Network with
                                                                                           VPN Access
       Tunneling Protocol. This protocol does not provide data encryption. Instead,
       it is designed to create end-to-end connections called tunnels through which
       data can travel. L2TP is actually a combination of two older protocols,
       one (called Layer 2 Forwarding Protocol, or L2FP) developed by Cisco, and
       the other (called Point-to-Point Tunneling Protocol, or PPTP) developed by
       Microsoft.

       Many VPNs today use a combination of L2TP and IPSec, called L2TP Over
       IPSec. This type of VPN combines the best features of L2TP and IPSec to pro-
       vide a high degree of security and reliability.



Understanding VPN Servers and Clients
       A VPN connection requires a VPN Server and a VPN Client — the server is
       the gatekeeper at one end of the tunnel, the client at the other. The main dif-
       ference between the server and the client is that it’s the client that initiates
       the connection with the server. A VPN client can establish a connection with
       just one server at a time. However, a server can accept connections from
       many clients.
218      Understanding VPN Servers and Clients


               Typically, the VPN server is a separate hardware device, most often a secu-
               rity appliance such as a Cisco ASA security appliance. VPN servers can also
               be implemented in software. For example, Windows Server 2008 includes
               built-in VPN capabilities, though they are not easy to configure. And a VPN
               server can be implemented in Linux as well.

               Figure 5-1 shows one of the many VPN configuration screens for a Cisco
               ASA appliance. This screen provides the configuration details for an IPSec
               VPN connection. The most important item of information on this screen is
               the Pre-Shared Key, which is used to encrypt the data sent over the VPN.
               The client will need to provide the identical key in order to participate in
               the VPN.




Figure 5-1:
An IPSec
configura-
tion page on
a Cisco ASA
security
appliance.



               A VPN client is usually software that runs on a client computer that wants to
               connect to the remote network. The VPN client software must be configured
               with the IP address of the VPN server as well as authentication information
               such as a username and the Pre-Shared Key that will be used to encrypt the
               data. If the key used by the client doesn’t match the key used by the server,
               the VPN server will reject the connection request from the client.
                                     Understanding VPN Servers and Clients          219

              Figure 5-2 shows a typical VPN software client. When the client is config-
              ured with the correct connection information (which you can do by click-
              ing the New button), you just click Connect. After a few moments, the VPN
              client will announce that the connection has been established and the VPN
              is connected.




Figure 5-2:
A VPN
client.



              A VPN client can also be a hardware device, like another security appliance.     Book III
              This is most common when the VPN is used to connect two networks at sep-        Chapter 5
              arate locations. For example, suppose your company has an office in Pixley
              and a second office in Hootersville. Each office has its own network with




                                                                                              Extending Your
                                                                                               Network with
              servers and client computers. The easiest way to connect these offices with




                                                                                               VPN Access
              a VPN would be to put an identical security appliance at each location. Then,
              you could configure the security appliances to communicate with each other
              over a VPN.
220   Book III: Network Administration and Security
Chapter 6: Managing
Network Software
In This Chapter
✓ Understanding the types of software licenses
✓ Using license servers
✓ Exploring the deployment options
✓ Keeping up to date with patches and service packs




A    n important task of any network administrator is managing the various
     bits and pieces of software that are used by your users throughout
the network. Most, if not all, of your network users will have a version of
Microsoft Office installed on their computers. Depending on the type of
business, other software may be widely used. For example, accounting firms
require accounting software; engineering firms require engineering soft-
ware; and the list goes on.

Long gone are the days when you could purchase one copy of a computer
program and freely install it on every computer on your network. Most soft-
ware has built-in features — commonly called copy protection — designed
to prevent such abuse. But even in the absence of copy protection, nearly
all software is sold with a license agreement that dictates how many com-
puters you can install and use the software on. As a result, managing soft-
ware licenses is an important part of network management.

Some software programs have a license feature that uses a server computer
to regulate the number of users who can run the software at the same time.
As the network administrator, your job is to set up the license server and
keep it running.

Another important aspect of managing software on the network is figuring
out the most expedient way to install the software on multiple computers.
The last thing you want to do is manually run the software’s Setup program
individually on each computer in your network. Instead, you’ll want to use
the network itself to aid in the deployment of the software.
222   Understanding Software Licenses


         Finally, you’ll want to ensure that all the software programs installed
         throughout your network are kept up to date with the latest patches and
         updates from the software vendors.

         This chapter elaborates on these aspects of network software management.



Understanding Software Licenses
         Contrary to popular belief, you don’t really buy software. Instead, you buy
         the right to use the software. When you purchase a computer program
         at a store, all you really own after you complete the purchase is the box
         the software comes in, the disks/discs the software is recorded on, and a
         license that grants you the right to use the software according to the terms
         offered by the software vendor. The software itself is still owned by the
         vendor.

         That means that you’re obligated to follow the terms of the license agree-
         ment that accompanies the software. Very few people actually read the com-
         plete text of a software agreement before they purchase and use software. If
         you do, you’ll find that a typical agreement contains restrictions, such as the
         following:

          ✦ You’re allowed to install the software on one and only one computer.
            Some license agreements have specific exceptions to this, allowing you
            to install the software on a single computer at work and a single com-
            puter at home, or on a single desktop computer and a single notebook
            computer, provided that both computers are used by the same person.
            However, most software licenses stick to the one-computer rule.
          ✦ The license agreement probably allows you to make a backup copy of
            the disks/discs. The number of backup copies you can make, though, is
            probably limited to one or two.
          ✦ You aren’t allowed to reverse-engineer the software. In other words,
            you can’t use programming tools to dissect the software in an effort to
            learn the secrets of how it works.
          ✦ Some software restricts the kinds of applications it can be used for.
            For example, you might purchase a student or home version of a pro-
            gram that prohibits commercial use. And some software — for example,
            Sun Microsystem’s Java — prohibits its use for military applications.
          ✦ Some software has export restrictions that prevent you from taking it
            out of the country.
                               Understanding Software Licenses          223

 ✦ Nearly all software licenses limit the liability of the software vendor
   to replacing defective installation disks/discs. In other words, the
   software vendor isn’t responsible for any damage that might be caused
   by bugs in the software. In a few cases, these license restrictions have
   been set aside in court, and companies have been held liable for damage
   caused by defective software. For the most part, though, you use soft-
   ware at your own risk.

In many cases, software vendors give you a choice of several different types
of licenses to choose from. When you purchase software for use on a net-
work, you need to be aware of the differences between these license types
so you can decide which type of license to get. The most common types are

 ✦ Retail: A retail license is the software you buy directly from the software
   vendor, a local store, or an online store. A retail software license usu-
   ally grants you the right for a single user to install and use the software.
   Depending on the agreement, the license may allow that user to install
   the software on two computers — one at work and one at home. The
   key point is that only one user may use the software. (However, it is
   usually acceptable to install the software on a computer that’s shared
   by several users. In that case, more than one user can use the software,
   provided they use it one at a time.)
    The main benefit of a retail license is that it stays with the user when       Book III
    the user upgrades his or her computer. In other words, if you get a new       Chapter 6
    computer, you can remove the software from your old computer and
    install it on your new computer.




                                                                                     Managing Network
 ✦ OEM: An OEM license is for software that’s installed by a computer man-




                                                                                        Software
   ufacturer on a new computer. (OEM stands for original equipment manu-
   facturer.) For example, if you purchase a computer from Dell and order
   Microsoft Office Professional along with the computer, you’re getting an
   OEM license. The most important thing to know about an OEM license
   is that it applies only to the specific computer for which you purchased
   the software. You are never allowed to install the software on any com-
   puter other than the one for which you purchased the software.
    Thus, if one day in a fit of rage you throw your computer out the fifth
    floor window of your office and the computer smashes into little pieces
    in the parking lot below, your OEM version of Office is essentially lost
    forever. When you buy a replacement computer, you’ll have to buy a
    new OEM license of Office for the new computer. You can’t install the
    old software on the new computer.
    If this sounds like a severe limitation, it is. However, OEM licenses are
    usually substantially less expensive than retail licenses. For example, a
    retail license of Microsoft Office 2007 Professional sells for about $500.
    The OEM version is less than $400.
224   Using a License Server


          ✦ Volume: A volume license allows you to install and use the software on
            more than one computer. The simplest type of volume license simply
            specifies how many computers on which you can install the software.
            For example, you might purchase a 20-user version of a program that
            allows you to install the software on 20 computers. Usually, you’re on
            the honor system to make sure that you don’t exceed the quantity. You
            want to set up some type of system to keep track of this type of software
            license. For example, you could create an Excel spreadsheet in which
            you record the name of each person for whom you install the software.
             Volume licenses can become considerably more complicated. For exam-
             ple, Microsoft offers several different types of volume license programs,
             each with different pricing and different features and benefits. Table 6-1
             summarizes the features of these license programs. For more informa-
             tion, refer to www.microsoft.com/licensing.



            Table 6-1                 Microsoft Volume License Plans
           Plan                Features
           Open License        Purchase as few as five end-user licenses.
           Open Value          Purchase as few as five end-user licenses and receive free
                               upgrades during the subscription term (three years).
           Select License      This is a licensing program designed for companies with 250
                               or more employees.
           Enterprise          This is an alternative to the Select License program that’s
                               designed to cost-effectively provide Windows Vista, Office,
                               and certain other programs throughout an organization of at
                               least 250 employees.


          ✦ Subscription: A subscription isn’t really a separate type of license but
            rather an optional add-on to a volume license. The added subscription
            fee entitles you to technical support and free product upgrades during
            the term of the subscription, which is usually annual. For some types
            of products, the subscription also includes periodic downloads of new
            data. For example, antivirus software usually includes a subscription
            that regularly updates your virus signature data. Without the subscrip-
            tion, the antivirus software would quickly become ineffective.



Using a License Server
         Some programs let you purchase network licenses that enable you to install
         the software on as many computers as you want, but regulate the number
         of people who can use the software at any given time. To control how many
                                           Using a License Server        225

people use the software, a special license server is set up. Whenever a user
starts the program, the program checks with the license server to see
whether a license is available. If so, the program is allowed to start, and the
number of available licenses on the license server is reduced by one. Later,
when the user quits the program, the license is returned to the server.

One of the most commonly used license server software is FlexLM, by
Macrovision. It is used by AutoCAD as well as by many other network
software applications. FlexLM uses special license files that are issued by
a software vendor to indicate how many licenses of a given product you
have purchased. Although the license file is a simple text file, its contents
are cryptic and generated by a program that only the software vendor has
access to. Here’s an example of a typical license file for AutoCAD:

SERVER server1 000ecd0fe359
    USE_SERVER
    VENDOR adskflex port=2080
    INCREMENT 57000ARDES_2010_0F adskflex 1.000 permanent 6 \
            VENDOR_STRING=commercial:permanent BORROW=4320 SUPERSEDE \
            DUP_GROUP=UH ISSUED=07-May-2007 SN=339-71570316 SIGN=”102D \
            85EC 1DFE D083 B85A 46BB AFB1 33AE 00BD 975C 8F5C 5ABC 4C2F \
            F88C 9120 0FB1 E122 BA97 BCAE CC90 899F 99BB 23C9 CAB5 613F \
            E7BB CA28 7DBF 8F51 3B21” SIGN2=”033A 6451 5EEB 3CA4 98B8 F92C \
            184A D2BC BA97 BCAE CC90 899F 2EF6 0B45 A707 B897 11E3 096E 0288 \
            787C 997B 0E2E F88C 9120 0FB1 782C 00BD 975C 8F5C 74B9 8BC1”
                                                                                   Book III
(Don’t get any crazy ideas here. I changed the numbers in this license file so    Chapter 6
that it won’t actually work. I’m not crazy enough to publish an actual valid
AutoCAD license file!)




                                                                                     Managing Network
                                                                                        Software
One drawback to software that uses a license server is that you have to
take special steps to run the software when the server isn’t available. For
example, what if you have AutoCAD installed on a notebook computer and
you want to use it while you’re away from the office? In that case, you have
two options:

 ✦ Use virtual private network (VPN) software to connect to the network.
   After you’re connected with the VPN, the license server will be available
   so you can use the software.
 ✦ Borrow a license. When you borrow a license, you can use the software
   for a limited period of time while you’re disconnected from the network.
   Of course, the borrowed license is subtracted from the number of avail-
   able licenses on the server.

In most cases, the license server is a mission-critical application — as impor-
tant as any other function on your network. If the license server goes down,
all users who depend on it will be unable to work. Don’t worry; they’ll let you
know. They’ll be lining up outside your door demanding to know when you
can get the license server up and running so they can get back to work.
226   Options for Deploying Network Software


         Because the license server provides such an important function, treat it with
         special care. Make sure that the license server software runs on a stable,
         well-maintained server computer. Don’t load up the license server computer
         with a bunch of other server functions.

         And make sure that it’s backed up. If possible, install the license server soft-
         ware on a second server computer as a backup. That way, if the main license
         server computer goes down and you can’t get it back up and running, you
         can quickly switch over to the backup license server.



Options for Deploying Network Software
         After you acquire the correct license for your software, the next task of the
         network administrator is deploying the software — that is, installing the
         software on your users’ computers and configuring the software so that it
         runs efficiently on your network. The following sections describe several
         approaches to deploying software to your network.


         Deploying software manually
         Most software is shipped on CD or DVD media along with a Setup program
         that you run to install the software. The Setup program usually asks you a
         series of questions, such as where you want the program installed, whether
         you want to install all of the program’s features or just the most commonly
         used features, and so on. You may also be required to enter a serial number,
         registration number, license key, or other code that proves you purchased
         the software. When all these questions are answered, the Setup program
         then installs the program.

         If only a few of your network users will be using a particular program, the
         Setup program may be the most convenient way to deploy the program.
         Just take the installation media with you to the computer you want to
         install the program on, insert the disc into the CD/DVD drive, and run the
         Setup program.

         When you finish manually installing software from a CD or DVD, don’t forget
         to remove the disc from the drive! It’s easy to leave the disc in the drive,
         and if the user rarely or never uses the drive, it might be weeks or months
         before anyone discovers that the disc is missing. By that time, you’ll be hard
         pressed to remember where it is.


         Running Setup from a network share
         If you plan on installing a program on more than two or three computers
         on your network, you’ll find it much easier to run the Setup program from a
         network share rather than from the original CDs or DVDs. To do so, follow
         these steps:
                        Options for Deploying Network Software          227

1. Create a network share and a folder within the share where you can
    store the Setup program and other files required to install the program.
    I usually set up a share named Software and then create a separate
    folder in this share for each program I want to make available from the
    network. You should enable Read access for all network users, but allow
    full access only for yourself and your fellow administrators.
2. Copy the entire contents of the program’s CD or DVD to the folder you
    create in Step 1.
    To do so, insert the CD or DVD in your computer’s CD/DVD drive. Then,
    use Windows Explorer to select the entire contents of the disc and drag
    it to the folder you create in Step 1.
    Alternatively, you can choose Start➪Run and enter cmd to open a com-
    mand prompt. Then, enter a command, such as this:
       xcopy d:\*.* \\server1\software\someprogram\*.* /s
    In this example, d: is the drive letter of your CD/DVD drive, server1 is
    the name of your file server, and software and someprogram are the
    names of the share and folder you created in Step 1.
3. To install the program on a client computer, open a Windows Explorer
    window, navigate to the share and folder you create in Step 1, and
    double-click the Setup.exe file.                                              Book III
                                                                                 Chapter 6
    This launches the Setup program.
4. Follow the instructions displayed by the Setup program.




                                                                                    Managing Network
    When the Setup program is finished, the software is ready to use.




                                                                                       Software
Copying the Setup program to a network share spares you the annoyance
of carrying the installation discs to each computer you want to install the
software on. It doesn’t spare you the annoyance of purchasing a valid license
for each computer! It’s illegal to install the software on more computers than
the license you acquired from the vendor allows.


Installing silently
Copying the contents of a program’s installation media to a network share
spares you the annoyance of carrying the installation discs from computer
to computer, but you still have to run the Setup program and answer all its
annoying questions on every computer. Wouldn’t it be great if there were a
way to automate the Setup program so that after you run it, it runs without
any further interaction from you? With many programs, you can.

In some cases, the Setup program itself has a command line switch that
causes it to run silently. You can usually find out what command line
switches are available by entering the following at a command prompt:

setup /?
228   Options for Deploying Network Software


         With luck, you’ll find that the Setup program itself has a switch, such as /
         quiet or /silent, that installs the program with no interaction, using the
         program’s default settings.

         If the Setup program doesn’t offer any command line switches, don’t despair!
         The following procedure describes a technique that often lets you silently
         install the software:

          1. Open an Explorer window and navigate to
              • Windows 7 and Vista: C:\Users\name\AppData\Local\Temp
              • Windows XP: C:\Documents and Settings\name\Local
                Settings\Temp
             Then, delete the entire contents of this folder.
             This is the Temporary folder where various programs deposit tempo-
             rary files. Windows may not allow you to delete every file in this folder,
             but it’s a good idea to begin this procedure by emptying the Temp folder
             as much as possible.
          2. Run the Setup program and follow the installation steps right up to the
             final step.
             When you get to the confirmation screen that says the program is about
             ready to install the software, stop! Don’t click the OK or Finish button.
          3. Return to the Temp folder you open in Step 1, and then poke around
             until you find the .msi file created by the Setup program you run in
             Step 2.
             The .msi file is the actual Windows Installer program that Setup runs to
             install the program. It may have a cryptic name, such as 84993882.msi.
          4. Copy the .msi file to the network share from which you want to
             install the program on your client computers.
             For example, \\server1\software\someprogram.
          5. Rename the .msi file to setup.msi.
             This step is optional, but I prefer to run setup.msi rather than
             84993882.msi.
          6. Use Notepad to create a batch file to run the .msi file with the /quiet
             switch.
             To create the batch file
             a. Right-click in the folder where the .msi file is stored.
             b. Choose New➪Text Document.
             c. Change the name of the text document to Setup.bat.
                       Options for Deploying Network Software           229

    d. Right-click the Setup.bat file and choose Edit.
    e. Add the following line to the file:
       setup.msi /quiet
7. Save the file.
    You can now install the software by navigating to the folder you created
    the setup.bat file in and double-clicking the setup.bat file.


Creating an administrative installation image
Some software, such as Microsoft Office and AutoCAD, comes with tools
that let you create a fully configured silent setup program that you can then
use to silently install the software. For Microsoft software, this silent setup
program is called an administrative installation image. (Note that the OEM
versions of Microsoft Office don’t include this feature. You need to purchase
a volume license to create an administrative installation.)

To create an administrative image, you simply run the configuration tool
supplied by the vendor. The configuration tool lets you choose the installa-
tion options you want to have applied when the software is installed. Then,
it creates a network setup program on a network share that you specify. You
can then install the software on a client computer by opening an Explorer
window, navigating to the network share where you saved the network setup          Book III
program, and running the network setup program.                                   Chapter 6




                                                                                     Managing Network
Pushing out software with group policy




                                                                                        Software
One final option you should consider for network software deployment is
using Windows Group Policy to automatically install software to network
users. Group Policy is a feature of Windows Server 2003 and 2007 that lets
you create policies that are assigned to users. You use the Windows Group
Policy feature to specify that certain users should have certain software pro-
grams available to them.

Note that group policies aren’t actually assigned to individual users, but to
Organizational Units (OUs), which are used to categorize users in Active
Directory. Thus, you might create a Group Policy to specify that everyone in
the Accounting Department OU should have Microsoft Excel.

Then, whenever anyone in the Accounting Department logs on to Windows,
Windows checks to make sure that Excel is installed on the user’s com-
puter. If Excel is not installed, Windows advertises Excel on the computer.
Advertising software on a computer means that a small portion of the soft-
ware is downloaded to the computer — just enough to display an icon for
the program on the Start menu and to associate Excel with the Excel file
extensions (such as .xls).
230   Keeping Software Up to Date


         If the user clicks the Start menu icon for the advertised application or
         attempts to open a document that’s associated with the advertised applica-
         tion, the application is automatically installed on the user’s computer. The
         user will have to wait a few minutes while the application is installed, but the
         installation is automatic.

         For more information about setting up group policy software installation,
         search Google or any other search engine for “Group Policy Software.”



Keeping Software Up to Date
         One of the annoyances that every network manager faces is applying soft-
         ware patches to keep the operating system and other software up to date.
         A software patch is a minor update that fixes the small glitches that crop
         up from time to time, such as minor security or performance issues. These
         glitches aren’t significant enough to merit a new version of the software, but
         they’re important enough to require fixing. Most of the patches correct secu-
         rity flaws that computer hackers have uncovered in their relentless attempts
         to wreak havoc on the computer world.

         Periodically, all the recently released patches are combined into a service
         pack. Although the most diligent network administrators apply all patches
         when they’re released, many administrators just wait for the service packs.

         Windows includes a feature called Windows Update that automatically
         installs patches and service packs when they become available. These
         patches apply not just to Windows but to other Microsoft software as well.
         To use Windows Update, open the Control Panel, click System and Security,
         then click Windows Update. A window appears, such as the one shown in
         Figure 6-1.

         From the Windows Update window, you can click the Install Updates button
         to download any updates that apply to your computer. You can also config-
         ure Windows Update so that it automatically checks for updates and installs
         them without asking. To set this option, click the Change Settings link. This
         displays the Windows Update Change Settings page, as shown in Figure 6-2.

         The Important Updates drop-down list gives you several options for auto-
         matic operation:

          ✦ Install Updates Automatically: This option checks for updates on a reg-
            ular basis and installs them without asking. You can specify how often to
            check for updates and at what time.
                                              Keeping Software Up to Date        231




Figure 6-1:
Windows
Update.




                                                                                            Book III
                                                                                           Chapter 6




                                                                                              Managing Network
                                                                                                 Software
Figure 6-2:
Changing
the
Windows
Update
settings.



              ✦ Download Updates But Let Me Choose Whether to Install Them: If you’re
                a picky computer user, you should choose this option. It automatically
                downloads the updates but then gives you the option of whether or not to
                install them. This lets you opt out of updates you may not want.
232   Keeping Software Up to Date


          ✦ Check for Updates But Let Me Choose Whether to Download and
            Install Them: This option lets you determine which updates should be
            downloaded.
          ✦ Never Check for Updates: This option disables automatic updates
            altogether.
Chapter 7: Solving Network
Problems
In This Chapter
✓ Checking the obvious things
✓ Fixing computers that have expired
✓ Pinpointing the cause of trouble
✓ Restarting client and server computers
✓ Reviewing network event logs
✓ Keeping a record of network woes




F   ace it: Networks are prone to breaking.


They have too many parts. Cables. Connectors. Cards. Switches. Routers.
All these parts must be held together in a delicate balance, and the network
equilibrium is all too easy to disturb. Even the best-designed computer net-
works sometimes act as if they’re held together with baling wire, chewing
gum, and duct tape.

To make matters worse, networks breed suspicion. After your computer is
attached to a network, users begin to blame the network every time some-
thing goes wrong, regardless of whether the problem has anything to do
with the network. You can’t get columns to line up in a Word document?
Must be the network. Your spreadsheet doesn’t add up? The @@#$% net-
work’s acting up again. The stock market’s down? Arghhh!!!!!!

The worst thing about network failures is that sometimes they can shut
down an entire company. It’s not so bad if just one user can’t access a par-
ticular shared folder on a file server. If a critical server goes down, however,
your network users may be locked out of their files, applications, e-mail, and
everything else they need to conduct business as usual. When that happens,
they’ll be beating down your doors and won’t stop until you get the network
back up and running.

In this chapter, I review some of the most likely causes of network trouble
and suggest some basic troubleshooting techniques that you can employ
when your network goes on the fritz.
234   When Bad Things Happen to Good Computers


When Bad Things Happen to Good Computers
         The following are some basic troubleshooting steps explaining what you
         should examine at the first sign of network trouble. In many (if not most)
         of the cases, one of the following steps can get your network back up and
         running:

         1. Make sure that your computer and everything attached to it is
             plugged in.
             Computer geeks love it when a user calls for help and they get to tell the
             user that the computer isn’t plugged in or that its power strip is turned
             off. They write it down in their geek logs so that they can tell their
             geek friends about it later. They may even want to take your picture so
             that they can show it to their geek friends. (Most “accidents” involving
             computer geeks are a direct result of this kind of behavior. So try to be
             tactful when you ask a user whether he or she is sure the computer is
             actually turned on.)
         2. Make sure that your computer is properly connected to the network.
         3. Note any error messages that appear on the screen.
         4. Try restarting the computer.
             An amazing number of computer problems are cleared up by a simple
             restart of the computer. Of course, in many cases, the problem recurs,
             so you’ll have to eventually isolate the cause and fix the problem. Some
             problems are only intermittent, and a simple reboot is all that’s needed.
         5. Try the built-in Windows network troubleshooter.
             For more information, see the section, “Using the Windows Networking
             Troubleshooter,” later in this chapter.
         6. Check the free disk space on your computer and on the server.
             When a computer runs out of disk space or comes close to it, strange
             things can happen. Sometimes you get a clear error message indicating
             such a situation, but not always. Sometimes the computer just grinds to a
             halt; operations that used to take a few seconds now take a few minutes.
         7. Do a little experimenting to find out whether the problem is indeed a
             network problem or just a problem with the computer itself.
             See the section, “Time to Experiment,” later in this chapter, for some
             simple things that you can do to isolate a network problem.
         8. Try restarting the network server.
             See the section, “Restarting a Network Server,” later in this chapter.
                                                Fixing Dead Computers        235

Fixing Dead Computers
      If a computer seems totally dead, here are some things to check:

       ✦ Make sure that the computer is plugged in.
       ✦ If the computer is plugged into a surge protector or a power strip,
         make sure that the surge protector or power strip is plugged in and
         turned on. If the surge protector or power strip has a light, it should be
         glowing.
       ✦ Make sure that the computer’s On/Off switch is turned on. This advice
         sounds too basic to even include here, but many computers have two
         power switches: an on/off switch on the back of the computer, and a
         push-button on the front that actually starts the computer. If you push
         the front button and nothing happens, check the switch on the back to
         make sure it’s in the ON position.
          To complicate matters, newer computers have a Sleep feature, in which
          they appear to be turned off but really they’re just sleeping. All you have
          to do to wake such a computer is jiggle the mouse a little. (I used to have
          an uncle like that.) It’s easy to assume that the computer is turned off,
          press the power button, wonder why nothing happened, and then press
          the power button and hold it down, hoping it will take. If you hold down
          the power button long enough, the computer will actually turn itself off.      Book III
          Then, when you turn the computer back on, you get a message saying            Chapter 7
          the computer wasn’t shut down properly. Arghhh! The moral of the
          story is to jiggle the mouse if the computer seems to have nodded off.




                                                                                           Solving Network
       ✦ If you think the computer isn’t plugged in but it looks like it is, listen




                                                                                              Problems
         for the fan. If the fan is running, the computer is getting power, and the
         problem is more serious than an unplugged power cord. (If the fan isn’t
         running but the computer is plugged in and the power is on, the fan may
         be out to lunch.)
       ✦ If the computer is plugged in, turned on, and still not running, plug a
         lamp into the outlet to make sure that power is getting to the outlet.
         You may need to reset a tripped circuit breaker or replace a bad surge
         protector. Or you may need to call the power company. (If you live in
         California, don’t bother calling the power company. It probably won’t do
         any good.)
       ✦ Check the surge protector. Surge protectors have a limited life span.
         After a few years of use, many surge protectors continue to provide elec-
         trical power for your computer, but the components that protect your
         computer from power surges no longer work. If you’re using a surge
         protector that is more than two or three years old, replace the old surge
         protector with a new one.
236   Ways to Check a Network Connection


          ✦ Make sure that the monitor is plugged in and turned on. The monitor
            has a separate power cord and switch. (The monitor actually has two
            cables that must be plugged in. One runs from the back of the monitor
            to the back of the computer; the other is a power cord that comes from
            the back of the monitor and must be plugged into an electrical outlet.)
          ✦ Make sure that all cables are plugged in securely. Your keyboard, mon-
            itor, mouse, and printer are all connected to the back of your computer
            by cables.
             Make sure that the other ends of the monitor and printer cables are
             plugged in properly, too.
          ✦ If the computer is running but the display is dark, try adjusting the
            monitor’s contrast and brightness. Some monitors have knobs that you
            can use to adjust the contrast and brightness of the monitor’s display.
            They may have been turned down all the way.



Ways to Check a Network Connection
         The cables that connect client computers to the rest of the network are
         finicky beasts. They can break at a moment’s notice, and by “break,” I don’t
         necessarily mean “to physically break in two.” Although some broken cables
         look like someone got to the cable with pruning shears, most cable problems
         aren’t visible to the naked eye.

          ✦ Twisted-pair cable: If your network uses twisted-pair cable, you can
            quickly tell whether the cable connection to the network is good by
            looking at the back of your computer. Look for a small light located near
            where the cable plugs in; if this light is glowing steadily, the cable is
            good. If the light is dark or it’s flashing intermittently, you have a cable
            problem (or a problem with the network card or the hub or switch that
            the other end of the cable is plugged in to).
             If the light isn’t glowing steadily, try removing the cable from your com-
             puter and reinserting it. This action may cure the weak connection.
          ✦ Patch cable: Hopefully, your network is wired so that each computer is
            connected to the network with a short (six feet or so) patch cable. One
            end of the patch cable plugs into the computer, and the other end plugs
            into a cable connector mounted on the wall. Try quickly disconnecting
            and reconnecting the patch cable. If that doesn’t do the trick, try to find
            a spare patch cable that you can use.
          ✦ Switches: Switches are prone to having cable problems, too — especially
            switches that are wired in a “professional manner,” involving a rat’s nest
            of patch cables. Be careful whenever you enter the lair of the rat’s nest. If
            you need to replace a patch cable, be very careful when you disconnect
            the suspected bad cable and reconnect the good cable in its place.
                              Double-Checking Your Network Settings            237

A Bunch of Error Messages Just Flew By!
       Error messages that display when your computer boots can provide invalu-
       able clues to determine the source of the problem.

       If you see error messages when you start up the computer, keep the follow-
       ing points in mind:

        ✦ Don’t panic if you see a lot of error messages. Sometimes, a simple
          problem that’s easy to correct can cause a plethora of error messages
          when you start your computer. The messages may look as if your com-
          puter is falling to pieces, but the fix may be very simple.
        ✦ If the messages fly by so fast that you can’t see them, press your com-
          puter’s Pause key. Your computer comes to a screeching halt, giving
          you a chance to catch up on your error-message reading. After you’ve
          read enough, press the Pause key again to get things moving. (On key-
          boards that don’t have a Pause key, pressing Ctrl+Num Lock or Ctrl+S
          does the same thing.)
        ✦ If you miss the error messages the first time, restart the computer and
          watch them again.
        ✦ Better yet, press F8 when you see the Starting Windows message. This
          displays a menu that allows you to select from several startup options,       Book III
          including one that processes each line of your CONFIG.SYS file sepa-         Chapter 7
          rately so that you can see the messages displayed by each command
          before proceeding to the next command.




                                                                                          Solving Network
                                                                                             Problems
Double-Checking Your Network Settings
       I swear that there are little green men who sneak into offices at night, turn
       on computers, and mess up TCP/IP configuration settings just for kicks.
       These little green men are affectionately known as networchons.

       Remarkably, network configuration settings sometimes get inadvertently
       changed so that a computer, which enjoyed the network for months or even
       years, one day finds itself unable to access the network. So one of the first
       things you do, after making sure that the computers are actually on and that
       the cables aren’t broken, is a basic review of the computer’s network set-
       tings. Check the following:

        ✦ At a command prompt, run ipconfig to make sure that TCP/IP is up
          and running on the computer and that the IP addresses, subnet masks,
          and default gateway settings look right.
        ✦ Call up the network connection’s Properties dialog box and make sure
          that the necessary protocols are installed correctly.
238     Using the Windows Networking Troubleshooter


               ✦ Open the System Properties dialog box (double-click System in
                 Control Panel) and check the Computer Name tab.
                  Make sure that the computer name is unique and that the domain or
                  workgroup name is spelled properly.
               ✦ Double-check the user account to make sure that the user really has
                 permission to access the resources he or she needs.

              For more information about network configuration settings, see Book II,
              Chapters 3 and 6.



Using the Windows Networking Troubleshooter
              Windows comes with a built-in troubleshooter that can often help you to pin
              down the cause of a network problem. Figure 7-1 shows the Windows 7 ver-
              sion. Answer the questions asked by the troubleshooter and click Next to
              move from screen to screen. The Networking Troubleshooter can’t solve all
              networking problems, but it does point out the causes of the most common
              problems.




Figure 7-1:
The
Windows 7
Networking
Trouble-
shooter.
                                                     Time to Experiment       239

       The procedure for starting Networking Troubleshooter depends on which
       version of Windows you’re using:

        ✦ Windows 7: Open the Control Panel, click View Network Status and
          Tasks, and then click Troubleshoot Problems. Then select the trouble-
          shooter that seems most directly related to the problem you’re experi-
          encing. You’ll find troubleshooters for wireless network problems, home
          networks, and local area network (LAN) and Internet connections.
        ✦ Windows Vista: Choose Start➪Help and Support, click Troubleshooting,
          and then click the link for the network troubleshooter that seems most
          directly related to the problem you’re experiencing. You’ll find trouble-
          shooters for wireless network problems, home networks, and local area
          network (LAN) and Internet connections.
        ✦ Windows XP: Choose Start➪Help and Support➪Networking and the
          Web➪Fixing Network or Web Problems. Then click Home and Small
          Office Networking Troubleshooter.



Time to Experiment
       If you can’t find some obvious explanation for your troubles — like the com-
       puter is unplugged — you need to do some experimenting to narrow down
                                                                                         Book III
       the possibilities. Design your experiments to answer one basic question: Is it
                                                                                        Chapter 7
       a network problem or a local computer problem?




                                                                                           Solving Network
       Here are some ways you can narrow down the cause of the problem:




                                                                                              Problems
        ✦ Try performing the same operation on someone else’s computer. If no
          one on the network can access a network drive or printer, something is
          probably wrong with the network. On the other hand, if the error occurs
          on only one computer, the problem is likely with that computer. The
          wayward computer may not be reliably communicating with the network
          or configured properly for the network, or the problem may have noth-
          ing to do with the network at all.
        ✦ If you’re able to perform the operation on another computer with-
          out problems, try logging on to the network with another computer
          using your own username. Then see whether you can perform the
          operation without error. If you can, the problem is probably on your
          computer. If you can’t, the problem may be with the way your user
          account is configured.
        ✦ If you can’t log on at another computer, try waiting for a bit. Your
          account may be temporarily locked out. This can happen for a variety of
          reasons — the most common of which is trying to log on with the wrong
          password several times in a row. If you’re still locked out an hour later,
          call the network administrator and offer a doughnut.
240   Who’s on First?


Who’s on First?
         When troubleshooting a networking problem, it’s often useful to find out
         who is actually logged on to a network server. For example, if a user can’t
         access a file on the server, you can check whether the user is logged on.
         If so, you know that the user’s account is valid, but the user may not have
         permission to access the particular file or folder that he’s attempting to
         access. On the other hand, if the user isn’t logged on, the problem may
         lie with the account itself or how the user is attempting to connect to the
         server.

         It’s also useful to find out who’s logged on in the event that you need to
         restart the server. For more information about restarting a server, see the
         section, “Restarting a Network Server,” later in this chapter.

         To find out who is currently logged on to a Windows server, right-click the
         Computer icon on the desktop (My Computer in Windows Server 2003,
         Computer in Windows Server 2008) and choose Manage from the menu that
         appears. This brings up the Computer Management window. Open System
         Tools in the tree list and then open Shared Folders and select Sessions. A list
         of users who are logged on appears.

         You can immediately disconnect all users by right-clicking Sessions in the
         Computer Management window and choosing All Tasks➪Disconnect All.



Restarting a Client Computer
         Sometimes, trouble gets a computer so tied up in knots that the only thing
         you can do is reboot. In some cases, the computer just starts acting weird.
         Strange characters appear on the screen, or Windows goes haywire and
         doesn’t let you exit a program. Sometimes, the computer gets so confused
         that it can’t even move. It just sits there, like a deer staring at oncoming
         headlights. It won’t move, no matter how hard you press Esc or Enter. You
         can move the mouse all over your desktop, or you can even throw it across
         the room, but the mouse pointer on the screen stays perfectly still.

         When a computer starts acting strange, you need to reboot. If you must
         reboot, you should do so as cleanly as possible. I know this procedure may
         seem elementary, but the technique for safely restarting a client computer is
         worth repeating, even if it is basic:

          1. Save your work if you can.
                                    Restarting a Client Computer        241

    Use the File➪Save command to save any documents or files that you
    were editing when things started to go haywire. If you can’t use the
    menus, try clicking the Save button on the toolbar. If that doesn’t
    work, try pressing Ctrl+S (the standard keyboard shortcut for the Save
    command).
2. Close any running programs if you can.
    Use the File➪Exit command or click the Close button in the upper-right
    corner of the program window. Or press Alt+F4.
3. Restart the computer.
     • Windows XP: Choose Start➪Turn Off Computer to summon the
       Shut Down Windows dialog box. Select the Restart option, and then
       click OK.
     • Windows 7 and Vista: Click the Start button, click the right arrow that
       appears at the bottom-right corner of the Start menu, and then click
       Restart.

If restarting your computer doesn’t seem to fix the problem, you may need
to turn your computer off and then turn it on again. To do so, follow the pre-
vious procedure but choose Shut Down instead of Restart.

Here are a few things to try if you have trouble restarting your computer:          Book III
                                                                                   Chapter 7
1. If your computer refuses to respond to the Start➪Shut Down com-
    mand, try pressing Ctrl+Alt+Delete.




                                                                                      Solving Network
    This is called the “three-finger salute.” It’s appropriate to say, “Queueue”




                                                                                         Problems
    while you do it.
    When you press Ctrl+Alt+Delete, Windows displays a dialog box that
    enables you to close any running programs or shut down your computer
    entirely.
2. If pressing Ctrl+Alt+Delete doesn’t do anything, you’ve reached the
    last resort. The only thing left to do is turn off the computer by press-
    ing the power On/Off button and holding it down for a few seconds.
    Turning off your computer by pressing the power button is a drastic
    action that you should take only after your computer becomes com-
    pletely unresponsive. Any work you haven’t yet saved to disk is lost.
    (Sniff.) (If your computer doesn’t have a Reset button, turn off the com-
    puter, wait a few moments, and then turn the computer back on again.)

If at all possible, save your work before restarting your computer. Any work
you haven’t saved is lost. Unfortunately, if your computer is totally tied up in
knots, you probably can’t save your work. In that case, you have no choice
but to push your computer off the digital cliff.
242   Booting in Safe Mode


Booting in Safe Mode
         Windows provides a special start-up mode called Safe Mode that’s designed
         to help fix misbehaving computers. When you start your computer in Safe
         Mode, Windows loads only the most essential parts of itself into memory —
         the bare minimum required for Windows to work. Safe Mode is especially
         useful when your computer has developed a problem that prevents you
         from using the computer at all.

         To boot your computer in Safe Mode, first restart the computer. Then, as
         soon as the computer begins to restart, start pressing the F8 key — just tap
         away at it until a menu titled Advanced Boot Options appears. One of the
         options on this menu is Safe Mode; use the up- or down-arrow keys to select
         that option and then press Enter to boot in Safe Mode.



Using System Restore
         System Restore is a Windows feature that periodically saves important
         Windows configuration information and allows you to later return your
         system to a previously saved configuration. This can often fix problems by
         reverting your computer to a time when it was working.

         By default, Windows saves restore points whenever you install new software
         on your computer or apply a system update. Restore points are also saved
         automatically every seven days.

         Although System Restore is turned on by default, you should verify that
         System Restore is active and running to make sure that System Restore
         points are being created. To do that, right-click Computer in the Start menu,
         choose Properties, and then click the System Protection tab. The dialog
         box shown in Figure 7-2 is displayed. Verify that the Protection status for
         your computer’s C: drive is “On.” If it isn’t, select the C: drive and click the
         Configure button to configure System Restore for the drive.

         If your computer develops a problem, you can restore it to a previously
         saved restore point by clicking System Restore the System Protection tab.
         This brings up the System Restore Wizard, as shown in Figure 7-3. This
         wizard allows you to select the restore point you want to use.

         Here are a few additional thoughts to remember about System Restore:

          ✦ System Restore does not delete data files from your system. Thus, files in
            your Documents folder won’t be lost.
                                                       Using System Restore       243




Figure 7-2:
The System
Protection
tab of the
System
Properties
dialog box.




                                                                                           Book III
                                                                                          Chapter 7




                                                                                             Solving Network
Figure 7-3:




                                                                                                Problems
Using
System
Restore to
restore your
system to
an earlier
configura-
tion.



               ✦ System Restore does remove any applications or system updates you
                 have installed since the time the restore point was made. Thus, you
                 will need to re-install those applications or system updates — unless,
                 of course, you determine that an application or system update was the
                 cause of your problem in the first place.
               ✦ System Restore automatically restarts your computer. The restart may
                 be slow because some of the changes made by System Restore happen
                 after the restart.
244     Restarting Network Services


                ✦ Do not turn off or cut power to your computer during System Restore.
                  Doing so may leave your computer in an unrecoverable state.


Restarting Network Services
               Once in awhile, the operating system service that supports the task that’s
               causing you trouble inexplicably stops or gets stuck. If users can’t access a
               server, it may be because one of the key network services has stopped or is
               stuck.

               You can review the status of services by using the Services tool, as shown in
               Figure 7-4. To display it, right-click Computer on the Start menu and choose
               Manage; then, expand the Services and Applications node and click Services.
               Review this list to make sure that all key services are running. If an impor-
               tant service is paused or stopped, restart it.




Figure 7-4:
Looking at
services
(Windows 7).



               Which services qualify as “important” depends on what roles you define for
               the server. Table 7-1 lists a few important services that are common to most
               Windows network operating systems. However, many servers require addi-
               tional services besides these. In fact, a typical server will have many dozens
               of services running simultaneously.
                                             Restarting a Network Server              245

         Table 7-1                       Key Windows Services
         Service           Description
         Computer          Maintains a list of computers on the network that can be
         Browser           accessed. If this service is disabled, the computer won’t be
                           able to use browsing services, such as My Network Places.
         DHCP Client       Enables the computer to obtain its IP address from a Dynamic
                           Host Configuration Protocol (DHCP) server. If this service is
                           disabled, the computer’s Internet Protocol (IP) address won’t
                           be configured properly.
         DNS Client        Enables the computer to access a Domain Name Server
                           (DNS) server to resolve DNS names. If this service is disabled,
                           the computer won’t be able to handle DNS names, including
                           Internet addresses and Active Directory names.
         Server            Provides basic file- and printer-sharing services for the server.
                           If this service is stopped, clients won’t be able to connect to
                           the server to access files or printers.
         Workstation       Enables the computer to establish client connections with
                           other servers. If this service is disabled, the computer won’t
                           be able to connect to other servers.
                                                                                                Book III
                                                                                               Chapter 7
       Key services usually stop for a reason, so simply restarting a stopped ser-
       vice probably won’t solve your network’s problem — at least, not for long.




                                                                                                  Solving Network
       You should review the System log to look for any error messages that may




                                                                                                     Problems
       explain why the service stopped in the first place.



Restarting a Network Server
       Sometimes, the only way to flush out a network problem is to restart the net-
       work server that’s experiencing trouble.

       Restarting a network server is something you should do only as a last
       resort. Windows Server is designed to run for months or even years at a
       time without rebooting. Restarting a server invariably results in a temporary
       shutdown of the network. If you must restart a server, try to do it during off
       hours if possible.

       Before you restart a server, check whether a specific service that’s required
       has been paused or stopped. You may be able to just restart the individual
       service rather than the entire server. For more information, see the section,
       “Restarting Network Services,” earlier in this chapter.
246   Looking at Event Logs


         Here’s the basic procedure for restarting a network server:

          1. Make sure that everyone is logged off the server.
             The easiest way to do that is to restart the server after normal business
             hours, when everyone has gone home for the day. Then, you can just
             shut down the server and let the shutdown process forcibly log off any
             remaining users.
             To find out who’s logged on, refer to the earlier section, “Who’s on
             First?”
          2. After you’re sure the users have logged off, shut down the network
             server.
             You want to do this step behaving like a good citizen if possible —
             decently, and in order. Use the Star➪Shut Down command to shut
             down the server. This summons a dialog box that requires you to indi-
             cate the reason for the shutdown. The information you supply here is
             entered into the server’s System log, which you can review by using
             Event Viewer.
          3. Reboot the server computer or turn it off and then on again.
             Watch the server start up to make sure that no error messages appear.
          4. Tell everyone to log back on and make sure that everyone can now
             access the network.

         Remember the following when you consider restarting the network server:

          ✦ Restarting the network server is more drastic than restarting a client
            computer. Make sure that everyone saves his or her work and logs
            off the network before you do it! You can cause major problems if you
            blindly turn off the server computer while users are logged on.
          ✦ Obviously, restarting a network server is a major inconvenience to
            every network user. Better offer treats.



Looking at Event Logs
         One of the most useful troubleshooting techniques for diagnosing net-
         work problems is to review the network operating system’s built-in event
         logs. These logs contain information about interesting and potentially
         troublesome events that occur during the daily operation of your network.
         Ordinarily, these logs run in the background, quietly gathering information
         about network events. When something goes wrong, you can check the logs
                                   Documenting Your Trials and Tribulations           247

              to see whether the problem generated a noteworthy event. In many cases,
              the event logs contain an entry that pinpoints the exact cause of the prob-
              lem and suggests a solution.

              To display the event logs in a Windows server, use Event Viewer, which is
              available from the Administrative Tools menu. For example, Figure 7-5 shows
              an Event Viewer from a Windows Server 2008 system. The tree listing on
              the left side of Event Viewer lists five categories of events that are tracked:
              Application, Security, System, Directory Service, and File Replication Service.
              Select one of these options to see the log that you want to view. For details
              about a particular event, double-click the event to display a dialog box with
              detailed information about the event.




                                                                                                 Book III
                                                                                                Chapter 7


Figure 7-5:




                                                                                                   Solving Network
Event




                                                                                                      Problems
Viewer.




Documenting Your Trials and Tribulations
              For a large network, you probably want to invest in problem-management
              software that tracks each problem through the entire process of trouble-
              shooting, from initial report to final resolution. For small- and medium-sized
              networks, it’s probably sufficient to put together a three-ring binder with
              pre-printed forms. Or record your log in a Word document or an Excel
              spreadsheet.

              Regardless of how you track your network problems, the tracking log should
              include the following information:
248   Documenting Your Trials and Tribulations


          ✦ The real name and the network username of the person reporting the
            problem
          ✦ The date the problem was first reported
          ✦ An indication of the severity of the problem
             Is it merely an inconvenience, or is a user unable to complete his or her
             work because of the problem? Does a workaround exist?
          ✦ The name of the person assigned to resolve the problem
          ✦ A description of the problem
          ✦ A list of the software involved, including versions
          ✦ A description of the steps taken to solve the problem
          ✦ A description of any intermediate steps that were taken to try to solve
            the problem, along with an indication of whether those steps were
            “undone” when they didn’t help solve the problem
          ✦ The date the problem was finally resolved
      Chapter 8: Network Performance
      Anxiety
      In This Chapter
      ✓ Understanding performance problems
      ✓ Looking at bottlenecks
      ✓ Developing a procedure for solving performance problems
      ✓ Monitoring performance
      ✓ Implementing other tips for speeding up your network




      T    he term network performance refers to how efficiently the network
           responds to users’ needs. It goes without saying that any access to
      resources that involves a network will be slower than similar access that
      doesn’t involve a network. For example, it takes longer to open a Word
      document that resides on a network file server than it takes to open a simi-
      lar document that resides on a user’s local hard drive. However, it shouldn’t
      take much longer. If it does, you have a network performance problem.

      This chapter is a general introduction to the practice of tuning your network
      so that it performs as well as possible. Keep in mind that many specific bits
      of network tuning advice are scattered throughout this book. In this chap-
      ter, you can find some specific techniques for analyzing your network’s per-
      formance, taking corrective action when a performance problem develops,
      and charting your progress.



Why Administrators Hate Performance Problems
      Network performance problems are among the most difficult network prob-
      lems to track down and solve. If a user simply can’t access the network, it
      usually doesn’t take long to figure out why: A cable is broken, a network
      card or hub is malfunctioning, a user doesn’t have permission to access the
      resource, and so on. After a little investigation, the problem usually reveals
      itself. You fix it and move on to the next problem.
250   What Exactly Is a Bottleneck?


         Unfortunately, performance problems are messier. Here are just a few of the
         reasons that network administrators hate performance problems:

          ✦ Performance problems are difficult to quantify. Exactly how much
            slower is the network now than it was a week ago, a month ago, or even
            a year ago? Sometimes the network just feels slow, but you can’t quite
            define exactly how slow it really is.
          ✦ Performance problems usually develop gradually. Sometimes, a net-
            work slows down suddenly and drastically. More often, though, the net-
            work gradually gets slower, a little bit at a time, until one day when the
            users notice that the network is slooow.
          ✦ Performance problems often go unreported. Users gripe about the
            problem to each other around the water cooler, but they don’t for-
            mally contact you to let you know that their network seems 10 percent
            slower than usual. As long as they can still access the network, they just
            assume that the problem is temporary or just in their imaginations.
          ✦ Many performance problems are intermittent. Sometimes, a user
            calls you and complains that a certain network operation has become
            slower than molasses — and by the time you get to the user’s desk,
            the operation performs like a snap. Sometimes, you can find a pattern
            to the intermittent behavior, such as it’s slower in the morning than in
            the afternoon, or it’s only slow while backups are running or while the
            printer is working. Other times, you can’t find a pattern. Sometimes the
            operation is slow; sometimes it isn’t.
          ✦ Performance tuning is not an exact science. Improving performance
            sometimes involves educated guesswork. Will upgrading all the users
            from 100 Mbps to gigabit Ethernet improve performance? Probably.
            Will segmenting the network improve performance? Maybe. Will adding
            another 4GB of RAM to the server improve performance? Hopefully.
          ✦ The solution to performance problems is sometimes a hard sell. If a
            user can’t access the network because of a malfunctioning component,
            there’s usually not much question that the purchase of a replacement is
            justified. However, if the network is slow and you think you can fix it by
            upgrading the entire network to gigabit Ethernet, you may have trouble
            selling management on the upgrade.



What Exactly Is a Bottleneck?
         The term bottleneck does not in any way refer to the physique of your typi-
         cal computer geek. (Well, I guess it could, in some cases.) Rather, computer
         geeks coined the phrase when they discovered that the tapered shape of a
         bottle of Jolt Cola limited the rate at which they could consume the beverage.
                                 What Exactly Is a Bottleneck?         251

“Hey,” a computer geek said one day, “the gently tapered narrowness of this
bottle’s neck imposes a distinct limiting effect upon the rate at which I can
consume the tasty caffeine-laden beverage contained within. This draws to
mind a hitherto undiscovered yet obvious analogy to the limiting effect that a
single slow component of a computer system can have upon the performance
of the system as a whole.”

“Fascinating,” replied all the other computer geeks, who were fortunate
enough to be present at that historic moment.

The term stuck and is used to this day to draw attention to the simple fact
that a computer system is only as fast as its slowest component. It’s the
computer equivalent of the old truism that a chain is only as strong as its
weakest link.

For a simple demonstration of this concept, consider what happens when
you print a word processing document on a slow printer. Your word pro-
cessing program reads the data from disk and sends it to the printer. Then
you sit and wait while the printer prints the document.

Would buying a faster CPU or adding more memory make the document
print faster? No. The CPU is already much faster than the printer, and your
computer already has more than enough memory to print the document.
The printer itself is the bottleneck, so the only way to print the document       Book III
faster is to replace the slow printer with a faster one.                         Chapter 8


Here are some other random thoughts about bottlenecks:




                                                                                 Performance
                                                                                   Network
                                                                                   Anxiety
 ✦ A computer system always has a bottleneck. For example, suppose that
   you decided that the bottleneck on your file server is a slow IDE hard
   drive, so you replace it with the fastest SCSI drive money can buy. Now,
   the hard drive is no longer the bottleneck: The drive can process infor-
   mation faster than the controller card to which the disk is connected.
   You haven’t really eliminated the bottleneck: You just moved it from the
   hard drive to the disk controller. No matter what you do, the computer
   will always have some component that limits the overall performance of
   the system.
 ✦ One way to limit the effect of a bottleneck is to avoid waiting for the
   bottleneck. For example, print spooling lets you avoid waiting for a slow
   printer. Spooling doesn’t speed up the printer, but it does free you to do
   other work while the printer chugs along. Similarly, disk caching lets you
   avoid waiting for a slow hard drive.
 ✦ One of the reasons computer geeks are switching from Jolt Cola to
   Snapple is that Snapple bottles have wider necks.
252   The Five Most Common Network Bottlenecks


The Five Most Common Network Bottlenecks
         Direct from the home office in sunny Fresno, California, here are the ten —
         oops, five — most common network bottlenecks, in no particular order.


         The hardware inside your servers
         Your servers should be powerful computers capable of handling all the work
         your network will throw at them. Don’t cut corners by using a bottom-of-the-
         line computer that you bought at a discount computer store.

         The following are the four most important components of your server
         hardware:

          ✦ Processor: Your server should have a powerful processor. As a general
            rule, any processor that’s available in a $500 computer from a store
            that sells TVs and washing machines as well as computers is not a
            processor that you want to see in your file server. In other words,
            avoid processors that are designed for consumer-grade home comput-
            ers. For optimum performance, your servers should use server-class
            Itanium or Xeon processors.
          ✦ Memory: You can’t have too much memory. Memory is cheap, so don’t
            skimp. Don’t even think about running a server with less than 8GB of RAM.
          ✦ Disk: Don’t mess around with inexpensive SATA hard drives. To be
            respectable, you should have nothing but SCSI drives.
          ✦ Network interface: A $9.95 network card might be fine for your home
            network, but don’t use one in a file server that supports 50 users and
            then expect to be happy with the server’s performance. Remember that
            the server computer uses the network a lot more than any of the clients,
            so equip your servers with good network cards.


         The server’s configuration options
         All network operating systems have options that you can configure. Some
         of these options can make the difference between a pokey network and a
         zippy network. Unfortunately, no hard-and-fast rules exist for setting these
         options. Otherwise, you wouldn’t have options.

         The following are some of the more important tuning options available for
         most servers:
                  The Five Most Common Network Bottlenecks              253

 ✦ Virtual memory options: Virtual memory refers to disk paging files that
   the server uses when it doesn’t have enough real memory to do its work.
   Few servers ever have enough real memory, so virtual memory is always
   an important server feature. You can specify the size and location of the
   virtual memory paging files. For best performance, you should provide
   at least 1.5 times the amount of real memory. For example, if you have
   16GB of real memory, allocate at least 24GB of virtual memory. If neces-
   sary, you can increase this size later.
 ✦ Disk striping: Use Disk Defragmenter to optimize the data storage on
   your server’s disks. If the server has more than one hard drive, you
   can increase performance by creating striped volumes, which allow
   disk I/O operations to run concurrently on each of the drives in the
   stripe set.
 ✦ Network protocols: Make sure that your network protocols are config-
   ured correctly; remove any protocols that aren’t necessary.
 ✦ Free disk space on the server: Servers like to have plenty of breath-
   ing room on their disks. If the amount of free disk space on your server
   drops precipitously low, the server chokes up and slows to a crawl.
   Make sure that your server has plenty of space: A few dozen GBs of
   unused disk space provide a healthy buffer.


Servers that do too much                                                          Book III
                                                                                 Chapter 8
One common source of network performance problems is servers that are
overloaded with too many duties. Just because modern network operating
systems come equipped with dozens of different types of services doesn’t




                                                                                 Performance
                                                                                   Network
mean that you should enable and use them all on a single server. If a single




                                                                                   Anxiety
server is bogged down because of too much work, add a second server
to relieve the first server of some of its chores. Remember the old saying:
“Many hands make light work.”

For example, if your network needs more disk space, consider adding
a second file server rather than adding another drive to the server that
already has four drives that are nearly full. Or better yet, purchase a file
server appliance that is dedicated just to the task of serving files.

As a side benefit, your network will be easier to administer and more reliable
if you place separate functions on separate servers. For example, if you have
a single server that doubles as a file server and a mail server, you’ll lose
both services if you have to take down the server to perform an upgrade or
254   The Five Most Common Network Bottlenecks


         repair a failed component. However, if you have separate file and mail server
         computers, only one of the services will be interrupted if you have to take
         down one of the servers.


         The network infrastructure
         A network infrastructure comprises the cables and any switches, hubs, rout-
         ers, and other components that sit between your clients and your servers.
         The following network infrastructure items can slow down your network:

          ✦ Switches: Because switches are so inexpensive now, you can afford-
            ably solve a lot of performance problems by replacing outdated hubs
            with switches. Using switches instead of hubs reduces the overall load
            on your network. Also, make sure that your switches can handle the
            performance requirements of your network. For best performance, the
            switches should have gigabit ports.
          ✦ Segment sizes: Keep the number of computers and other devices on
            each network segment to a reasonable number. About 20 devices is
            usually the right number. (Note that if you replace your old hubs with
            switches, you instantly cut the size of each segment because each port
            on a switch constitutes a separate segment.)
          ✦ The network’s speed: If you have an older network, you’ll probably dis-
            cover that many — if not all — of your users are still working at 100 Mbps.
            Upgrading to gigabit speed will speed up the network dramatically.
          ✦ The backbone speed: If your network uses a backbone to connect seg-
            ments, consider upgrading the backbone to 1 Gbps.

         The hardest part about improving the performance of a network is determin-
         ing what the bottlenecks are. With sophisticated test equipment and years of
         experience, network gurus can make pretty good educated guesses. Without
         the equipment and experience, you can still make pretty good uneducated
         guesses.


         Malfunctioning components
         Sometimes a malfunctioning network card or other component slows down
         the network. For example, a switch may malfunction intermittently, occa-
         sionally letting packets through but dropping enough of them to slow down
         the network. After you identify the faulty component, replacing it will restore
         the network to its original speed.
                          Tuning Your Network the Compulsive Way             255

Tuning Your Network the Compulsive Way
      You have two ways to tune your network. The first is to think about it a bit,
      take a guess at what may improve performance, try it, and see whether the
      network seems to run faster. This approach is how most people go about
      tuning the network.

      Then you have the compulsive way, which is suitable for people who orga-
      nize their sock drawers by color and their food cupboards alphabetically by
      food groups. The compulsive approach to tuning a network goes something
      like this:

       1. Establish a method for objectively testing the performance of some
          aspect of the network.
          This method is benchmarking, and the result of your benchmark is a
          baseline.
       2. Change one variable of your network configuration and rerun the test.
          For example, suppose you think that increasing the size of the disk
          cache can improve performance. Change the cache size, restart the
          server, and run the benchmark test. Note whether the performance
          improves, stays the same, or becomes worse.
                                                                                       Book III
       3. Repeat Step 2 for each variable that you want to test.                      Chapter 8

      Here are some salient points to keep in mind if you decide to tune your net-
      work the compulsive way:




                                                                                      Performance
                                                                                        Network
                                                                                        Anxiety
       ✦ If possible, test each variable separately. In other words, reverse the
         changes you made to other network variables before proceeding.
       ✦ Write down the results of each test. That way, you have an accurate
         record of the impact that each change made on your network’s
         performance.
       ✦ Be sure to change only one aspect of the network each time you run
         the benchmark. If you make several changes, you won’t know which one
         caused the change. One change may improve performance, but the other
         change may worsen performance so that the changes cancel each other
         out — kind of like offsetting penalties in a football game.
       ✦ If possible, conduct the baseline test during normal working hours.
         That way, the network is undergoing its normal workload.
       ✦ To establish your baseline performance, run your benchmark test two
         or three times to make sure that the results are repeatable.
256     Monitoring Network Performance


Monitoring Network Performance
               One way to monitor network performance is to use a stopwatch to see how
               long it actually takes to complete common network tasks, such as opening
               documents or printing reports. If you choose to monitor your network by
               using the stopwatch technique, you’ll want to get a clipboard, baseball cap,
               and gray sweat suit to complete the ensemble.

               A more high-tech approach to monitoring network performance is to use a
               monitor program that automatically gathers network statistics for you. After
               you set up the monitor, it plugs away, silently spying on your network and
               recording what it sees in performance logs. You can then review the perfor-
               mance logs to see how your network is doing.

               For large networks, you can purchase sophisticated monitoring programs
               that run on their own dedicated servers. For small- and medium-sized net-
               works, you can probably get by with the built-in monitoring facilities that
               come with the network operating system. For example, Figure 8-1 shows
               the Performance Monitor tool that comes with Windows Server 2003. Other
               operating systems come with similar tools.




Figure 8-1:
Monitoring
performance.



               Windows Performance Monitor lets you keep track of several different
               aspects of system performance at once. You track each performance aspect
               by setting up a counter. You can choose from dozens of different counters.
                               Monitoring Network Performance                 257

Table 8-1 describes some of the most commonly used counters. Note that
each counter refers to a server object, such as physical disk, memory, or the
processor.



  Table 8-1               Commonly Used Performance Counters
  Object        Counter         Description
  Physical      % Free          The percentage of free space on the server’s
  Disk          Space           physical disks. Should be at least 15 percent.
  Physical      Average         Indicates how many disk operations are waiting
  Disk          Queue           while the disk is busy servicing other disk opera-
  Length                        tions. Should be two or fewer.
  Memory        Pages/          The number of pages retrieved from the virtual
                second          memory page files per second. A typical thresh-
                                old is about 2,500 pages per second.
  Processor     % Processor     Indicates the percentage of the processor’s time
                Time            that it’s busy doing work rather than sitting idle.
                                Should be 85 percent or less.


Here are a few more things to consider about performance monitoring:                   Book III
                                                                                      Chapter 8
 ✦ Performance Monitor enables you to view real-time data or to view
   data that you can save in a log file. Real-time data gives you an idea




                                                                                      Performance
   about what’s happening with the network at a particular moment, but




                                                                                        Network
                                                                                        Anxiety
   the more useful information comes from the logs.
 ✦ You can schedule logging to occur at certain times of the day and for
   certain intervals. For example, you may schedule the log to gather data
   every 15 seconds from 9:00 to 9:30 every morning and then again from
   3:00 to 3:30 every afternoon.
 ✦ Even if you don’t have a performance problem now, you should set up
   performance logging and let it run for a few weeks to gather baseline
   data. If you develop a problem, this baseline data will prove invaluable
   while you research the problem.
 ✦ Don’t leave performance logging turned on all the time. Gathering
   performance data slows down your server. Use it only occasionally
   to gather baseline data or when you’re experiencing a performance
   problem.
258   More Performance Tips


More Performance Tips
         Here are a few last-minute performance tips that barely made it in:

          ✦ You can often find the source of a slow network by staring at the net-
            work hubs or switches for a few minutes. These devices have colorful
            arrays of green and red lights. The green lights flash whenever data is
            transmitted; the red lights flash when a collision occurs. An occasional
            red flash is normal, but if one or more of the red lights is flashing
            repeatedly, the network interface card (NIC) connected to that port
            may be faulty.
          ✦ Check for scheduled tasks, such as backups, batched database
            updates, or report jobs. If at all possible, schedule these tasks to run
            after normal business hours, such as at night when no one is in the
            office. These jobs tend to slow down the network by hogging the serv-
            er’s hard drives.
          ✦ Sometimes, faulty application programs can degrade performance.
            For example, some programs develop a memory leak: They use memory
            but then forget to release the memory after they finish. Programs
            with memory leaks can slowly eat up all the memory on a server, until
            the server runs out and grinds to a halt. If you think a program has a
            memory leak, contact the manufacturer of the program to see whether a
            fix is available.
          ✦ Spyware can slow a system to a crawl. A common source of performance
            problems on client computers is spyware, those annoying programs that
            you almost can’t help but pick up when you surf the Internet. Fortunately,
            you can remove spyware with a variety of free or inexpensive spyware
            removal tools. For more information, use Google or another search engine
            to search for spyware removal.
      Chapter 9: Backing Up Your Data
      In This Chapter
      ✓ Understanding the need for backups
      ✓ Working with tape drives and other backup media
      ✓ Understanding the different types of backups
      ✓ Mastering tape rotation and other details




      I  f you’re the hapless network manager, the safety of the data on your
         network is your responsibility. In fact, it’s your primary responsibility.
      You get paid to lie awake at night worrying about your data. Will it be there
      tomorrow? If it’s not, can you get it back? And — most importantly — if you
      can’t get it back, will you have a job tomorrow?

      This chapter covers the ins and outs of being a good, responsible, trust-
      worthy network manager. No one gives out merit badges for this stuff, but
      someone should.



Backing Up Your Data
      Having data backed up is the cornerstone of any disaster recovery plan.
      Without backups, a simple hard drive failure can set your company back
      days or even weeks while it tries to reconstruct lost data. In fact, without
      backups, your company’s very existence is in jeopardy.

      The main goal of a backup is simple: Keep a spare copy of your network’s
      critical data so that no matter what happens, you never lose more than one
      day’s work. The stock market may crash, hanging chads may factor into
      another presidential election, and George Lucas may decide to make a pre-
      prequel. When you stay on top of your backups, though, you’ll never lose
      more than one day’s work.

      The way to do this, naturally, is to make sure that data is backed up on a
      daily basis. For many networks, you can back up all the network hard drives
      every night. And even if full nightly backups aren’t possible, you can still use
      techniques that can ensure that every file on the network has a backup copy
      that’s no more than one day old.
260   All about Tapes and Tape Drives


All about Tapes and Tape Drives
         If you plan on backing up the data on your network server’s hard drives,
         you obviously need some type of media on which to back up the data. You
         could copy the data onto CDs, but a 500GB hard drive would need more than
         750 CDs to do a full backup. That’s a few more discs than most people want
         to keep in the closet. And you could use DVDs, but you’ll still need about
         a dozen of them as well as an hour or so to fill each one. Sigh. That means
         devoting a Saturday to creating your backup.

         Because of the limitations of CDs and DVDs, most network administrators
         back up network data to tape. Depending on the make and model of the tape
         drive, you can copy as much as 800GB of data onto a single tape.

         One of the benefits of tape backup is that you can run it unattended. In fact,
         you can schedule a tape backup to run automatically during off hours when
         no one is using the network. For unattended backups to work, though, you
         must ensure that you have enough tape capacity to back up your entire net-
         work server’s hard drive without having to manually switch tapes. If your
         network server has only 100GB of data, you can easily back it up onto a
         single tape. However, if you have 1,000GB of data, invest in a tape drive that
         features a magazine changer that can hold several tapes and automatically
         cycle them in and out of the drive. That way, you can run your backups
         unattended.

         Here are some additional thoughts concerning tape backups:

          ✦ Travan drives: A popular style of tape backup for small servers is a
            Travan drive, which comes in a variety of models with tape capacities
            ranging from 20GB to 40GB. You can purchase a 20GB drive for less
            than $200.
          ✦ DAT and DLT units: For larger networks, you can get tape backup units
            that offer higher capacity and faster backup speed than Travan drives —
            for more money, of course. Digital audio tape (DAT) units can back up as
            much as 80GB on a single tape, and DLT (digital linear tape) drives can
            store up to 800GB on one tape. DAT and DLT drives can cost $1,000 or
            more, depending on the capacity.
          ✦ Robotic units: If you’re really up the backup creek with hundreds of
            gigabytes to back up, you can get robotic tape backup units that auto-
            matically fetch and load tape cartridges from a library. That way, you
            can do complete backups without having to load tapes manually. As you
            can likely guess, these units aren’t inexpensive: Small ones, which have
            a library of about eight tapes and a total backup capacity of more than
            5,000GB, start at about $4,000.
                                                      Backup Software        261

Backup Software
      All versions of Windows come with a built-in backup program. In addition,
      most tape drives come with backup programs that are often faster or more
      flexible than the standard Windows backup.

      You can also purchase sophisticated backup programs that are specially
      designed for networks that have multiple servers with data that must be
      backed up. For a basic Windows file server, you can use the backup pro-
      gram that comes with Windows Server. Server versions of Windows come
      with a decent backup program that can run scheduled, unattended tape
      backups.

      Backup programs do more than just copy data from your hard drive to tape.
      Backup programs use special compression techniques to squeeze your data
      so that you can cram more data onto fewer tapes. Compression factors of
      2:1 are common, so you can usually squeeze 100GB of data onto a tape that
      would hold only 50GB of data without compression. (Tape drive manufac-
      turers tend to state the capacity of their drives by using compressed data,
      assuming a 2:1 compression ratio. Thus, a 200GB tape has an uncompressed
      capacity of 100GB.)

      Whether you achieve a compression factor of 2:1 depends on the nature of        Book III
      the data you’re backing up:                                                    Chapter 9

       ✦ Documents: If your network is used primarily for Office applications and
         is filled with Word and Excel documents, you’ll probably get better than




                                                                                        Backing Up
                                                                                         Your Data
         2:1 compression.
       ✦ Graphics: If your network data consists primarily of graphic image files,
         you probably won’t get much compression. Most graphic image file for-
         mats are already compressed, so they can’t be compressed much more
         by the backup software’s compression methods.

      Backup programs also help you keep track of which data has been backed
      up and which hasn’t. They also offer options, such as incremental or differ-
      ential backups that can streamline the backup process, as I describe in the
      next section.

      If your network has more than one server, invest in good backup software.
      The most popular is Yosemite Backup, made by BarracudaWare (www.
      barracudaware.com). Besides being able to handle multiple servers, one
      of the main advantages of backup software (such as Yosemite Backup) is
      that it can properly back up Microsoft Exchange server data.
262   Types of Backups


Types of Backups
         You can perform five different types of backups. Many backup schemes rely
         on full daily backups, but for some networks, using a scheme that relies on
         two or more of these backup types is more practical.

         The differences among the five types of backups involve a little technical
         detail known as the archive bit. The archive bit indicates whether a file has
         been modified since it was backed up. The archive bit is a little flag that’s
         stored along with the filename, creation date, and other directory informa-
         tion. Any time a program modifies a file, the archive bit is set to the On posi-
         tion. That way, backup programs know that the file has been modified and
         needs to be backed up.

         The differences among the various types of backups center around
         whether they use the archive bit to determine which files to back up as
         well as whether they flip the archive bit to the Off position after they back
         up a file. Table 9-1 summarizes these differences, which I explain in the
         following sections.

         Backup programs allow you to select any combination of drives and folders
         to back up. As a result, you can customize the file selection for a backup
         operation to suit your needs. For example, you can set up one backup plan
         that backs up all a server’s shared folders and drives plus its mail server
         stores but then leaves out folders that rarely change, such as the operating
         system folders or installed program folders. You can then back up those
         folders on a less regular basis. The drives and folders that you select for a
         backup operation are collectively called the backup selection.



           Table 9-1                    How Backup Types Use the Archive Bit
           Backup Type            Selects Files Based on     Resets Archive Bits After
                                  Archive Bit?               Backing Up?
           Normal                 No                         Yes
           Copy                   No                         No
           Daily                  No*                        No
           Incremental            Yes                        Yes
           Differential           Yes                        No
           *Selects files based on the Last Modified date.
                                                  Types of Backups        263

The archive bit would have made a good Abbott and Costello routine. (“All
right, I wanna know who modified the archive bit.” “What.” “Who?” “No,
what.” “Wait a minute . . . just tell me what’s the name of the guy who modi-
fied the archive bit!” “Right.”)


Normal backups
A normal backup — also called a full backup — is the basic type of backup. In
a normal backup, all files in the backup selection are backed up regardless of
whether the archive bit has been set. In other words, the files are backed up
even if they haven’t been modified since the last time they were backed up.
When each file is backed up, its archive bit is reset, so backups that select
files based on the archive bit setting won’t back up the files.

When a normal backup finishes, none of the files in the backup selection
have their archive bits set. As a result, if you immediately follow a normal
backup with an incremental backup or a differential backup, no files will be
selected for backup by the incremental or differential backup because no
files will have their archive bits set.

The easiest backup scheme is to simply schedule a normal backup every
night. That way, all your data is backed up on a daily basis. Then, if the need
arises, you can restore files from a single tape or set of tapes. Restoring files
is more complicated when other types of backups are involved.                        Book III
                                                                                    Chapter 9
Do normal backups nightly if you have the tape capacity to do them unat-
tended: that is, without having to swap tapes. If you can’t do an unattended




                                                                                       Backing Up
normal backup because the amount of data to be backed up is greater than




                                                                                        Your Data
the capacity of your tape drive(s), you have to use other types of backups in
combination with normal backups.

If you can’t get a normal backup on a single tape and you can’t afford a
second tape drive or a tape changer, take a hard look at the data that’s being
included in the backup selection. I recently worked on a network that was
difficult to back up onto a single tape. When I examined the data that was
being backed up, I discovered a large amount of static data that was essen-
tially an online archive of old projects. This data was necessary because
network users needed it for research purposes, but the data was read-only.
Even though the data never changed, it was being backed up to tape every
night, and the backups required two tapes. After we removed this data from
the cycle of nightly backups, the backups were able to squeeze onto a single
tape again.

If you remove static data from the nightly backup, make sure that you have a
secure backup of the static data on tape, CD-RW, or some other media.
264   Types of Backups


         Copy backups
         A copy backup is similar to a normal backup except that the archive bit isn’t
         reset when each file is copied. As a result, copy backups don’t disrupt the
         cycle of normal and incremental or differential backups.

         Copy backups are usually not incorporated into regular, scheduled backups.
         Instead, you use a copy backup when you want to do an occasional one-
         shot backup. For example, if you’re about to perform an operating system
         upgrade, you should back up the server before proceeding. If you do a full
         backup, the archive bits are reset, and your regular backups are disrupted.
         However, if you do a copy backup, the archive bits of any modified files
         remain unchanged. As a result, your regular normal and incremental or dif-
         ferential backups are unaffected.

         If you don’t incorporate incremental or differential backups into your
         backup routine, the difference between a copy backup and a normal backup
         is moot.


         Daily backups
         A daily backup backs up just those files that have been changed the same
         day when the backup is performed. A daily backup examines the modifica-
         tion date stored with each file’s directory entry to determine whether a file
         should be backed up. Daily backups don’t reset the archive bit.

         I’m not a big fan of this option because of the small possibility that some
         files may slip through the cracks. Someone may be working late one night
         and modify a file after the evening’s backups have completed — but before
         midnight — meaning that those files won’t be included in the following
         night’s backups. Incremental or differential backups, which rely on the
         archive bit rather than the modification date, are more reliable.


         Incremental backups
         An incremental backup backs up only those files that were modified since
         the last time you did a backup. Incremental backups are a lot faster than full
         backups because your network users probably modify only a small portion
         of the files on the server in any given day. As a result, if a full backup takes
         three tapes, you can probably fit an entire week’s worth of incremental back-
         ups on a single tape.

         When an incremental backup copies each file, it resets the file’s archive bit.
         That way, the file will be backed up again before your next normal backup
         only when a user modifies the file again.
                                                 Types of Backups        265

Here are some thoughts about using incremental backups:

 ✦ The easiest way to use incremental backups is the following:
     • A normal backup every Monday
       If your full backup takes more than 12 hours, you may want to do it
       on Friday so that it can run over the weekend.
     • An incremental backup on each remaining normal business day (for
       example, Tuesday, Wednesday, Thursday, and Friday)
 ✦ When you use incremental backups, the complete backup consists of
   the full backup tapes and all the incremental backup tapes that you’ve
   made since you did the full backup.
    If the hard drive crashes and you have to restore the data onto a new
    drive, you first restore Monday’s normal backup and then you restore
    each of the subsequent incremental backups.
 ✦ Incremental backups complicate restoring individual files because the
   most recent copy of the file may be on the full backup tape or on any
   of the incremental backups.
    Backup programs keep track of the location of the most recent version
    of each file in order to simplify the process.
 ✦ When you use incremental backups, you can choose whether you                   Book III
   want to                                                                       Chapter 9

     • Store each incremental backup on its own tape.




                                                                                    Backing Up
     • Append each backup to the end of an existing tape.




                                                                                     Your Data
    Often, you can use a single tape for a week of incremental backups.


Differential backups
A differential backup is similar to an incremental backup except that it
doesn’t reset the archive bit when files are backed up. As a result, each dif-
ferential backup represents the difference between the last normal backup
and the current state of the hard drive.

To do a full restore from a differential backup, you first restore the last
normal backup and then you restore the most recent differential backup.

For example, suppose that you do a normal backup on Monday and differ-
ential backups on Tuesday, Wednesday, and Thursday, and then your hard
drive crashes Friday morning. On Friday afternoon, you install a new hard
drive. To restore the data, you first restore the normal backup from Monday.
Then, you restore the differential backup from Thursday. The Tuesday and
Wednesday differential backups aren’t needed.
266   Local versus Network Backups


         The main difference between incremental and differential backups is that

          ✦ Incremental backups result in smaller and faster backups.
          ✦ Differential backups are easier to restore.
             If your users often ask you to restore individual files, consider using dif-
             ferential backups.



Local versus Network Backups
         When you back up network data, you have two basic approaches to running
         the backup software: You can perform a local backup, in which the backup
         software runs on the file server itself and backs up data to a tape drive that’s
         installed in the server. Or, you can perform a network backup, in which you
         use one network computer to back up data from another network computer.
         In a network backup, the data has to travel over the network to get to the
         computer that’s running the backup.

         If you run the backups from the file server, you’ll tie up the server while the
         backup is running — and users will complain that their server access has
         slowed to a snail’s pace. On the other hand, if you run the backup over the
         network from a client computer or a dedicated backup server, you’ll flood
         the network with gigabytes of data being backed up. Your users will then
         complain that the entire network has slowed to a snail’s pace.

         Network performance is one of the main reasons why you should try to
         run your backups during off hours, when other users aren’t accessing the
         network. Another reason to run backups during off hours is so that you can
         perform a more thorough backup. If you run your backup while other users
         are accessing files, the backup program is likely to skip over any files that
         are being accessed by users at the time the backup runs. As a result, your
         backup won’t include those files. Ironically, the files most likely to get left
         out of the backup are often the files that need backing up the most because
         they’re the files that are being used and modified.

         Here are some extra thoughts on client and server backups:

          ✦ Backing up directly from the server isn’t necessarily more efficient
            than backing up from a client because data doesn’t have to travel
            over the network. The network may well be faster than the tape drive.
            The network probably won’t slow down backups unless you back up
            during the busiest time of the day, when hordes of network users are
            storming the network gates.
                      How Many Sets of Backups Should You Keep?             267

       ✦ To improve network backup speed and to minimize the effect that net-
         work backups have on the rest of the network, consider using a 1,000
         Mbps switch instead of a normal 100 Mbps switch to connect the serv-
         ers and the backup client. That way, network traffic between the server
         and the backup client won’t bog down the rest of the network.
       ✦ Any files that are open while the backups are running won’t get backed
         up. That’s usually not a problem because backups are run at off hours
         when people have gone home. However, if someone leaves his computer
         on with a Word document open, that Word document won’t be backed up.
         One way to solve this problem is to set up the server so that it automati-
         cally logs everyone off the network before the backups begin.
       ✦ Some backup programs have special features that enable them to back
         up open files. For example, the Windows Server 2003 and 2008 backup
         programs do this by creating a snapshot of the volume when it begins,
         thus making temporary copies of any files that are modified during the
         backup. The backup backs up the temporary copies rather than the ver-
         sions being modified. When the backup finishes, the temporary copies
         are deleted.



How Many Sets of Backups Should You Keep?
                                                                                       Book III
      Don’t try to cut costs by purchasing one backup tape and reusing it every       Chapter 9
      day. What happens if you accidentally delete an important file on Tuesday
      and don’t discover your mistake until Thursday? Because the file didn’t exist
      on Wednesday, it won’t be on Wednesday’s backup tape. If you have only




                                                                                         Backing Up
                                                                                          Your Data
      one tape that’s reused every day, you’re outta luck.

      The safest scheme is to use a new backup tape every day and keep all your
      old tapes in a vault. Pretty soon, though, your tape vault can start looking
      like the warehouse where they stored the Ark of the Covenant at the end of
      Raiders of the Lost Ark.

      As a compromise between these two extremes, most users purchase several
      tapes and rotate them. That way, you always have several backup tapes to fall
      back on, just in case the file you need isn’t on the most recent backup tape.
      This technique is tape rotation, and several variations are commonly used:

       ✦ The simplest approach is to purchase three tapes and label them A, B,
         and C. You use the tapes on a daily basis in sequence: A the first day, B
         the second day, C the third day; then A the fourth day, B the fifth day,
         C the sixth day, and so on. On any given day, you have three genera-
         tions of backups: today’s, yesterday’s, and the day-before-yesterday’s.
         Computer geeks like to call these the grandfather, father, and son tapes.
268   A Word about Tape Reliability


          ✦ Another simple approach is to purchase five tapes and use one each
            day of the workweek.
          ✦ A variation of the preceding bullet is to buy eight tapes. Take four
            of them and write Tuesday on one label, Wednesday on the second,
            Thursday on the third, and Friday on the fourth label. On the other four
            tapes, write Monday 1, Monday 2, Monday 3, and Monday 4. Now, tack up
            a calendar on the wall near the computer and number all the Mondays in
            the year: 1, 2, 3, 4, 1, 2, 3, 4, and so on.
             On Tuesday through Friday, you use the appropriate daily backup tape.
             When you run a full backup on Monday, consult the calendar to decide
             which Monday tape to use. With this scheme, you always have four
             weeks’ worth of Monday backup tapes, plus individual backup tapes for
             the rest of the week.
          ✦ If bookkeeping data lives on the network, make a backup copy of all
            your files (or at least all your accounting files) immediately before
            closing the books each month; then retain those backups for each
            month of the year. This doesn’t necessarily mean that you should pur-
            chase 12 additional tapes. If you back up just your accounting files, you
            can probably fit all 12 months on a single tape. Just make sure that you
            back up with the “append to tape” option rather than the “erase tape”
            option so that the previous contents of the tape aren’t destroyed. Also,
            treat this accounting backup as completely separate from your normal
            daily backup routine.

         Keep at least one recent full backup at another location. That way, if your
         office should fall victim to an errant Scud missile or a rogue asteroid, you
         can re-create your data from the backup copy that you stored offsite. Make
         sure the person entrusted with the task of taking the backups to this off-site
         location is trustworthy.



A Word about Tape Reliability
         From experience, I’ve found that although tape drives are very reliable, they
         do run amok once in a while. The problem is that they don’t always tell you
         when they’re not working. A tape drive (especially the less-expensive Travan
         drives) can spin along for hours, pretending to back up your data — but in
         reality, your data isn’t being written reliably to the tape. In other words, a
         tape drive can trick you into thinking that your backups are working just
         fine. Then, when disaster strikes and you need your backup tapes, you may
         just discover that the tapes are worthless.

         Don’t panic! Here’s a simple way to assure yourself that your tape drive is
         working. Just activate the “compare after backup” feature of your backup
         software. Then, as soon as your backup program finishes backing up your
                                            About Cleaning the Heads         269

      data, it rewinds the tape, reads each backed-up file, and compares it with the
      original version on the hard drive. If all files compare, you know your back-
      ups are trustworthy.

      Here are some additional thoughts about the reliability of tapes:

       ✦ The compare-after-backup feature doubles the time required to do a
         backup, but that doesn’t matter if your entire backup fits on one tape.
         You can just run the backup after hours. Whether the backup and repair
         operation takes one hour or ten doesn’t matter, as long as it’s finished
         by the time the network users arrive at work the next morning.
       ✦ If your backups require more than one tape, you may not want to run
         the compare-after-backup feature every day. However, be sure to run it
         periodically to check that your tape drive is working.
       ✦ If your backup program reports errors, throw away the tape and use a
         new tape.
       ✦ Actually, you should ignore that last comment about waiting for your
         backup program to report errors. You should discard tapes before your
         backup program reports errors. Most experts recommend that you
         should use a tape only about 20 times before discarding it. If you use the
         same tape every day, replace it monthly. If you have tapes for each day
         of the week, replace them twice yearly. If you have more tapes than that,      Book III
         figure out a cycle that replaces tapes after about 20 uses.                   Chapter 9



About Cleaning the Heads




                                                                                          Backing Up
                                                                                           Your Data
      An important aspect of backup reliability is proper maintenance of your tape
      drives. Every time you back up to tape, little bits and specks of the tape rub
      off onto the read and write heads inside the tape drive. Eventually, the heads
      become too dirty to reliably read or write data.

      To counteract this problem, clean the tape heads regularly. The easiest way
      to clean them is to use a cleaning cartridge for the tape drive. The drive
      automatically recognizes when you insert a cleaning cartridge and then per-
      forms a routine that wipes the cleaning tape back and forth over the heads
      to clean them. When the cleaning routine is done, the tape is ejected. The
      whole process takes only about 30 seconds.

      Because the maintenance requirements of each drive differ, check the
      drive’s user’s manual to find out how and how often to clean the drive. As a
      general rule, clean the drives once weekly.
270   Backup Security


         The most annoying aspect of tape drive cleaning is that the cleaning car-
         tridges have a limited life span. And, unfortunately, if you insert a used-up
         cleaning cartridge, the drive accepts it and pretends to clean the drive. For
         this reason, keep track of how many times you used the cleaning cartridge
         and replace it as recommended by the manufacturer.



Backup Security
         Backups create an often-overlooked security exposure for your network.
         No matter how carefully you set up user accounts and enforce password
         policies, if any user (including a guest) can perform a backup of the system,
         that user may make an unauthorized backup. In addition, your backup tapes
         themselves are vulnerable to theft. As a result, make sure that your backup
         policies and procedures are secure by taking the following measures:

          ✦ Set up a user account for the user who does backups. Because this user
            account has backup permission for the entire server, guard its password
            carefully. Anyone who knows the username and password of the backup
            account can log on and bypass any security restrictions that you place
            on that user’s normal user ID.
          ✦ Counter potential security problems by restricting the backup user ID
            to a certain client and a certain time of the day. If you’re really clever
            (and paranoid), you can probably set up the backup user’s account so
            that the only program it can run is the backup program.
          ✦ Use encryption to protect the contents of your backup tapes.
          ✦ Secure the backup tapes in a safe location, such as, um, a safe.
Chapter 10: Disaster Recovery and
Business Continuity Planning
In This Chapter
✓ Realizing the need for backups
✓ Making a plan
✓ Practicing disaster recovery
✓ Remembering tape rotation and other details




O     n April Fools’ Day about 20 years ago, my colleagues and I discov-
      ered that some loser had broken into the office the night before and
pounded our computer equipment to death with a crowbar. (I’m not making
this up.)

Sitting on a shelf right next to the mangled piles of what used to be a Wang
minicomputer system was an undisturbed disk pack that contained the only
complete backup of all the information that was on the destroyed computer.
The vandal didn’t realize that one more swing of the crowbar would have
escalated this major inconvenience into a complete catastrophe. Sure, we
were up a creek until we could get the computer replaced. And in those
days, you couldn’t just walk into your local Computer Depot and buy a new
computer off the shelf — this was a Wang minicomputer system that had
to be specially ordered. After we had the new computer, though, a simple
restore from the backup disk brought us right back to where we were on
March 31. Without that backup, getting back on track would have taken
months.

I’ve been paranoid about disaster planning ever since. Before then, I thought
that disaster planning meant doing good backups. That’s a part of it, but I
can never forget the day we came within one swing of the crowbar of losing
everything. Vandals are probably much smarter now: They know to smash
the backup disks as well as the computers themselves. Being prepared for
disasters entails much more than just doing regular backups.

Nowadays, the trendy term for disaster planning is a business continuity plan
(BCP). I suppose the term disaster planning sounded too negative, like we
were planning for disasters to happen. The new term refocuses attention on
the more positive aspect of preparing a plan that will enable a business to
carry on with as little interruption as possible in the event of a disaster.
272   Assessing Different Types of Disasters


         For more in-depth information about this topic, please refer to IT Disaster
         Recovery Planning For Dummies by Peter Gregory.



Assessing Different Types of Disasters
         Disasters come in many shapes and sizes. Some types of disasters are more
         likely than others. For example, your building is more likely to be struck by
         lightning than to be hit by a comet. In some cases, the likelihood of a particu-
         lar type of disaster depends on where you’re located. For example, crippling
         snowstorms are more likely in New York than in Florida.

         In addition, the impact of each type of disaster varies from company to com-
         pany. What may be a disaster for one company may only be a mere incon-
         venience for another. For example, a law firm may tolerate a disruption in
         telephone service for a day or two. Loss of communication via phone would
         be a major inconvenience but not a disaster. To a telemarketing firm, how-
         ever, a day or two with the phones down is a more severe problem because
         the company’s revenue depends on the phones.

         One of the first steps in developing a business continuity plan is to assess
         the risk of the various types of disasters that may affect your organization.
         Weigh the likelihood of a disaster happening with the severity of the impact
         that the disaster would have. For example, a meteor crashing into your
         building would probably be pretty severe, but the odds of that happening
         are miniscule. On the other hand, the odds of your building being destroyed
         by fire are much higher, and the consequences of a devastating fire would be
         about the same as those from a meteor impact.

         The following sections describe the most common types of risks that most
         companies face. Notice throughout this discussion that although many of
         these risks are related to computers and network technology, some are not.
         The scope of business continuity planning is much larger than just computer
         technology.


         Environmental disasters
         Environmental disasters are what most people think of first when they think
         of disaster recovery. Some types of environmental disasters are regional.
         Others can happen pretty much anywhere.

          ✦ Fire: Fire is probably the first disaster that most people think of when
            they consider disaster planning. Fires can be caused by unsafe condi-
            tions; carelessness, such as electrical wiring that isn’t up to code; natu-
            ral causes, such as lightning strikes; or arson.
                         Assessing Different Types of Disasters         273

 ✦ Earthquakes: Not only can earthquakes cause structural damage to your
   building, but they can also disrupt the delivery of key services and utili-
   ties, such as water and power. Serious earthquakes are rare and unpre-
   dictable, but some areas experience them with more regularity than
   others. If your business is located in an area known for earthquakes,
   your BCP should consider how your company would deal with a devas-
   tating earthquake.
 ✦ Weather: Weather disasters can cause major disruption to your busi-
   ness. Moderate weather may close transportation systems so that your
   employees can’t get to work. Severe weather may damage your building
   or interrupt delivery of services, such as electricity and water.
 ✦ Water: Flooding can wreak havoc with electrical equipment, such as
   computers. If floodwaters get into your computer room, chances are
   good that the computer equipment will be totally destroyed. Flooding
   can be caused not only by bad weather but also by burst pipes or mal-
   functioning sprinklers.
 ✦ Lightning: Lightning storms can cause electrical damage to your com-
   puter and other electronic equipment from lightning strikes as well as
   surges in the local power supply.


Deliberate disasters                                                              Book III
Some disasters are the result of deliberate actions by others. For example       Chapter 10

 ✦ Intentional damage: Vandalism or arson may damage or destroy your




                                                                                 Continuity Planning

                                                                                 Disaster Recovery
   facilities or your computer systems. The vandalism or arson may be




                                                                                   and Business
   targeted at you specifically, by a disgruntled employee or customer, or it
   may be random. Either way, the effect is the same.
    Don’t neglect the possibility of sabotage. A disgruntled employee who
    gets hold of an administrator’s account and password can do all sorts of
    nasty things to your network.
 ✦ Theft: Theft is always a possibility. You may come to work someday to
   find that your servers or other computer equipment have been stolen.
 ✦ Terrorism: Terrorism used to be something that most Americans weren’t
   concerned about, but September 11, 2001, changed all that. No matter
   where you live in the world, the possibility of a terrorist attack is real.


Disruption of services
You may not realize just how much your business depends on the delivery
of services and utilities. A BCP should take into consideration how you will
deal with the loss of certain services:
274   Assessing Different Types of Disasters


          ✦ No juice: Electrical power is crucial for computers and other types
            of equipment. During a power failure once (I live in California, so I’m
            used to it), I discovered that I can’t even work with pencil and paper
            because all my pencil sharpeners are electric. Electrical outages are
            not uncommon, but the technology to deal with them is readily avail-
            able. UPS (uninterruptible power supply) equipment is reliable and
            inexpensive.
          ✦ No communications: Communication connections can be disrupted
            by many causes. A few years ago, a railroad overpass was constructed
            across the street from my office. One day, a backhoe cut through the
            phone lines, completely cutting off our phone service — including our
            Internet connection — for a day and a half.
          ✦ No water: An interruption in the water supply may not shut down your
            computers, but it can disrupt your business by forcing you to close your
            facility until the water supply is reestablished.


         Equipment failure
         Modern companies depend on many different types of equipment for their
         daily operations. The failure of any of these key systems can disrupt busi-
         ness until the systems are repaired:

          ✦ Computer equipment failure can obviously affect business operations.
          ✦ Air-conditioning systems are crucial to regulate temperatures, espe-
            cially in computer rooms. Computer equipment can be damaged if the
            temperature climbs too high.
          ✦ Elevators, automatic doors, and other equipment may also be neces-
            sary for your business.


         Other disasters
         You should assess many other potential disasters. Here are just a few:

          ✦ Labor disputes
          ✦ Loss of key staff because of resignation, injury, sickness, or death
          ✦ Workplace violence
          ✦ Public health issues, such as epidemics, mold infestations, and so on
          ✦ Loss of a key supplier
          ✦ Nearby disaster, such as a fire or police action across the street that
            results in your business being temporarily blocked off
                                   Analyzing the Impact of a Disaster       275

Analyzing the Impact of a Disaster
       With a good understanding of the types of disasters that can affect your
       business, you can turn your attention to the impact that these disasters can
       have on your business. The first step is to identify the key business pro-
       cesses that can be impacted by different types of disasters. These business
       processes are different for each company. For example, here are a few of the
       key business processes for a publishing company:

        ✦ Editorial processes, such as managing projects through the process of
          technical editing, copyediting, and production
        ✦ Acquisition processes, such as determining product development strat-
          egies, recruiting authors, and signing projects
        ✦ Human resource processes, such as payroll, hiring, employee review,
          and recruiting
        ✦ Marketing processes, including sales tracking, developing marketing
          materials, sponsoring sales conferences, exhibiting at trade events, and
          so on
        ✦ Sales and billing processes, such as filling customer orders, maintaining
          the company Web site, managing inventory, and handling payments
        ✦ Executive and financial processes, such as managing cash flow, secur-        Book III
          ing credit, raising capital, deciding when to go public, and deciding       Chapter 10
          when to buy a smaller publisher or sell out to a bigger publisher




                                                                                      Continuity Planning

                                                                                      Disaster Recovery
                                                                                        and Business
       The impact of a disruption to each of these processes will vary. One
       common way to assess the impact of business process loss is to rate the
       impact of various degrees of loss for each process. For example, you may
       rate the loss of each process for the following time frames:

        ✦ 0 to 2 hours
        ✦ 2 to 24 hours
        ✦ 1 to 2 days
        ✦ 2 days to 1 week
        ✦ More than 1 week

       For some business processes, an interruption of two hours or even one day
       may be minor. For other processes, even the loss of a few hours may be very
       costly.
276   Developing a Business Continuity Plan


Developing a Business Continuity Plan
         A BCP is simply a plan for how you will continue operation of your key busi-
         ness processes should the normal operation of the process fail. For example,
         if your primary office location is shut down for a week because of a major
         fire across the street, you won’t have to suspend operations if you have a
         business continuity plan in place.

         The key to a BCP is redundancy of each component that is essential to your
         business processes. These components include:

          ✦ Facilities: If your company already has multiple office locations, you
            may be able to temporarily squeeze into one of the other locations for
            the duration of the disaster. If not, you should secure arrangements in
            advance with a real estate broker so that you can quickly arrange an
            alternate location. By having an arrangement made in advance, you can
            move into an emergency location on a moment’s notice.
          ✦ Computer equipment: It doesn’t hurt to have a set of spare computers
            in storage somewhere so that you can dig them out to use in an emer-
            gency. Preferably, these computers would already have your critical
            software installed. The next best thing would be to have detailed plans
            available so that your IT staff can quickly install key software on new
            equipment to get your business up and running.
             Always keep a current set of backup tapes at an alternate location.
          ✦ Phones: Discuss emergency phone services in advance with your
            phone company. If you’re forced to move to another location on
            24-hour notice, how quickly can you get your phones up and running?
            And can you arrange to have your incoming toll-free calls forwarded to
            the new location?
          ✦ Staff: Unless you work for a government agency, you probably don’t
            have redundant employees. However, you can make arrangements in
            advance with a temp agency to provide clerical and administrative help
            on short notice.
          ✦ Stationery: This sounds like a small detail, but you should store a
            supply of all your key stationery products (letterhead, envelopes,
            invoices, statements, and so on) in a safe location. That way, if your
            main location is suddenly unavailable, you don’t have to wait a week to
            get new letterhead or invoices printed.
          ✦ Hard copy files: Keep a backup copy of important printed material (cus-
            tomer billing files, sales records, and so on) at an alternate location.
                                                      Holding a Fire Drill     277

Holding a Fire Drill
       Remember in grade school when the fire alarm would go off and your
       teacher would tell you and the other kids to calmly put down your work and
       walk out to the designated safe zone in an orderly fashion? Drills are impor-
       tant so that if a real fire occurs, you don’t run and scream and climb all over
       each other in order to be the first one to get out.

       Any disaster recovery plan is incomplete unless you test it to see whether it
       works. Testing doesn’t mean that you should burn your building down one
       day to see how long it takes you to get back up and running. You should,
       though, periodically simulate a disaster in order to prove to yourself and
       your staff that you can recover.

       The most basic type of disaster recovery drill is a simple test of your net-
       work backup procedures. You should periodically attempt to restore key
       files from your backup tapes just to make sure that you can. You achieve
       several benefits by restoring files on a regular basis:

        ✦ Tapes are unreliable. The only way to be sure that your tapes are work-
          ing is to periodically restore files from them.
        ✦ Backup programs are confusing to configure. I’ve seen people run
          backup jobs for years that don’t include all the data they think they’re        Book III
          backing up. Only when disaster strikes and they need to recover a key          Chapter 10
          file do they discover that the file isn’t included in the backup.




                                                                                         Continuity Planning

                                                                                         Disaster Recovery
        ✦ Restoring files can be a little confusing, especially when you use a




                                                                                           and Business
          combination of normal and incremental or differential backups. Add
          to that the pressure of having the head of the company watching over
          your shoulder while you try to recover a lost file. If you regularly con-
          duct file restore drills, you’ll familiarize yourself with the restore fea-
          tures of your backup software in a low-pressure situation. Then, you can
          easily restore files for real when the pressure’s on.

       You can also conduct walkthroughs of more serious disaster scenarios. For
       example, you can set aside a day to walk through moving your entire staff to
       an alternate location. You can double-check that all the backup equipment,
       documents, and data are available as planned. If something is missing, it’s
       better to find out now rather than while the fire department is still putting
       water on the last remaining hot spots in what used to be your office.
278   Book III: Network Administration and Security
        Book IV
TCP/IP and the Internet
Contents at a Glance
      Chapter 1: Introduction to TCP/IP and the Internet . . . . . . . . . . . . . . .281
      Chapter 2: Understanding IP Addresses . . . . . . . . . . . . . . . . . . . . . . . .289
      Chapter 3: Using DHCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .307
      Chapter 4: Using DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .321
      Chapter 5: Using FTP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .347
      Chapter 6: TCP/IP Tools and Commands . . . . . . . . . . . . . . . . . . . . . . . .371
       Chapter 1: Introduction to TCP/IP
       and the Internet
       In This Chapter
       ✓ Introducing the Internet
       ✓ Familiarizing yourself with TCP/IP standards
       ✓ Figuring out how TCP/IP lines up with the OSI reference model
       ✓ Discovering important TCP/IP applications




       N     ot too many years ago, Transmission Control Protocol/Internet
             Protocol (TCP/IP) was known primarily as the protocol of the
       Internet. The biggest challenge of getting a local area network (LAN) connected
       to the Internet was figuring out how to mesh TCP/IP with the proprietary
       protocols that were the basis of the LANs — most notably Internetwork
       Packet Exchange/Sequenced Packet Exchange (IPX/SPX) and NetBIOS
       Extended User Interface (NetBEUI). A few years ago, network administrators
       realized that they could save the trouble of combining TCP/IP with IPX/SPX
       and NetBEUI by eliminating IPX/SPX and NetBEUI from the equation altogether.
       As a result, TCP/IP is not just the protocol of the Internet now, but it’s also
       the protocol on which most LANs are based.

       This chapter is a gentle introduction to the Internet in general and the TCP/
       IP suite of protocols in particular. After I get the introductions out of the
       way, you’ll be able to focus more in-depth on the detailed TCP/IP informa-
       tion given in the remaining chapters of Book IV.



What Is the Internet?
       The Goliath of all computer networks, the Internet links hundreds of millions
       of computer users throughout the world. Strictly speaking, the Internet is a
       network of networks. It consists of tens of thousands of separate computer
       networks, all interlinked, so that a user on any of those networks can reach
       out and potentially touch a user on any of the other networks. This network
       of networks connects more than half a billion computers to each other.
       (That’s right, billion with a b.)
282    What Is the Internet?




                       Just how big is the Internet?
  Because the Internet is not owned or con-          Unfortunately, no one knows how many actual
  trolled by any one organization, no one knows      users are on the Internet. Each host can sup-
  how big the Internet really is. Several organi-    port a single user, or in the case of domains —
  zations do attempt to periodically determine       such as aol.com (America Online) or msn.
  the size of the Internet, including the Internet   com (MSN) — hundreds of thousands or
  Systems Consortium (ISC), which completed its      perhaps even millions of users. No one really
  last survey in July 2009. ISC found that more      knows. Still, the indisputable point is that the
  than 681 million host computers are connected      Internet is big and growing every day.
  to the Internet. The same survey showed a
                                                     If you’re already on the Net and are interested,
  mere 353 million hosts in July 2005, so the size
                                                     you can check up on the latest Internet statis-
  of the Internet almost doubled in four years.
                                                     tics from ISC by visiting its Web site at www.
  The first year the ISC did the survey (1993), it
                                                     isc.org.
  found only 1.3 million host computers.



            One of the official documents (RFC 2026) of the Internet Engineering Task
            Force (IETF) defines the Internet as “a loosely organized international
            collaboration of autonomous, interconnected networks.” Broken down
            piece by piece, this definition encompasses several key aspects of what the
            Internet is:

             ✦ Loosely organized: No single organization has authority over the
               Internet. As a result, the Internet is not highly organized. Online services,
               such as America Online or MSN, are owned and operated by individual
               companies that control exactly what content appears on the service and
               what software can be used with the service. No one exercises that kind of
               control over the Internet. As a result, you can find just about any kind
               of material imaginable on the Internet. No one guarantees the accuracy
               of information that you find on the Internet, so you have to be careful as
               you work your way through the labyrinth.
             ✦ International: Nearly 200 countries are represented on the Internet,
               from Afghanistan to Zimbabwe.
             ✦ Collaboration: The Internet exists only because many different
               organizations cooperate to provide the services and support needed to
               sustain it. For example, much of the software that drives the Internet is
               open-source software that’s developed collaboratively by programmers
               throughout the world, who constantly work to improve the code.
              ✦ Autonomous: The Internet community respects that organizations that
                join the Internet are free to make their own decisions about how they con-
                figure and operate their networks. Although legal issues sometimes boil
                up, for the most part, each player on the Internet operates independently.
                                               A Little Internet History     283

        ✦ Interconnected: The whole key to the Internet is the concept of
          interconnection, which uses standard protocols that enable networks to
          communicate with each other. Without the interconnection provided by
          the TCP/IP protocol, the Internet would not exist.
        ✦ Networks: The Internet would be completely unmanageable if it consisted
          of half a billion individual users, all interconnected. That’s why the
          Internet is often described as a network of networks. Most individual
          users on the Internet don’t access the Internet directly. Instead, they
          access the Internet indirectly through another network, which may be a
          LAN in a business or academic environment, or a dialup or broadband
          network provided by an Internet service provider (ISP). In each case,
          however, the users of the local network access the Internet via a gateway
          IP router.
           The Internet is composed of several distinct types of networks:
           Government agencies, such as the Library of Congress and the White
           House; military sites (did you ever see War Games or any of the
           Terminator movies?); educational institutions, such as universities and
           colleges (and their libraries); businesses, such as Microsoft and IBM;
           ISPs, which allow individuals to access the Internet; and commercial
           online services, such as America Online and MSN.



A Little Internet History
       The Internet has a fascinating history, if such things interest you. There’s
       no particular reason why you should be interested in such things, of course,
       except that a superficial understanding of how the Internet got started may
       help you to understand and cope with the way this massive computer net-
       work exists today. So here goes.

       The Internet traces its beginnings back to a small network called ARPANET,
       built by the Department of Defense in 1969 to link defense installations.
       ARPANET soon expanded to include not only defense installations but uni-
       versities as well. In the 1970s, ARPANET was split into two networks: one for    Book IV
       military use (renamed MILNET) and the original ARPANET (for nonmilitary         Chapter 1
       use). The two networks were connected by a networking link called IP — the         Introduction to TCP/
                                                                                           IP and the Internet

       Internet protocol — so called because it allowed communication between two
       networks.

       The good folks who designed IP had the foresight to realize that, soon,
       more than two networks would want to be connected. In fact, they left room
       for tens of thousands of networks to join the game, which is a good thing
       because it wasn’t long before the Internet began to take off.

       By the mid-1980s, ARPANET was beginning to reach the limits of what it
       could do. Enter the National Science Foundation (NSF), which set up a
       nationwide network designed to provide access to huge supercomputers,
       those monolithic computers used to discover new prime numbers and
284   TCP/IP Standards and RFCs


         calculate the orbits of distant galaxies. The supercomputers were never put
         to much use, but the network that was put together to support the super-
         computers — NSFNET — was used. In fact, NSFNET replaced ARPANET as
         the new backbone for the Internet.

         Then, out of the blue, it seemed as if the whole world became interested in
         the Internet. Stories about it appeared in Time and Newsweek. Any company
         that had “dot com” in its name practically doubled in value every month. Al
         Gore claimed he invented the Internet. The Net began to grow so fast that
         even NSFNET couldn’t keep up, so private commercial networks got into
         the game. The size of the Internet nearly doubled every year for most of the
         1990s. Then, in the first few years of the millennium, the growth rate slowed
         a bit. However, the Internet still seems to be growing at the phenomenal rate
         of about 30 to 50 percent per year, and who knows how long this dizzying
         rate of growth will continue.



TCP/IP Standards and RFCs
         The TCP/IP protocol standards that define how the Internet works are
         managed by the IETF. However, the IETF doesn’t impose standards. Instead,
         it simply oversees the process by which ideas are developed into agreed-upon
         standards.

         An Internet standard is published in the Request for Comments (RFC)
         document. When a document is accepted for publication, it is assigned an
         RFC number by the IETF. The RFC is then published. After it’s published, an
         RFC is never changed. If a standard is enhanced, the enhancement is covered
         in a separate RFC.

         At the time of this writing, more than 3,500 RFCs were available from the
         IETF Web site (www.ietf.org). The oldest RFC is RFC 0001, published in
         April, 1969. It describes how the host computers communicated with each
         other in the original ARPANET. The most recent RFC (as of February, 2010) is
         RFC 5777, a proposed standard entitled “Traffic Classification and Quality of
         Service (QoS) Attributes for Diameter.”

         Not all RFCs represent Internet standards. The following paragraphs
         summarize the various types of RFC documents:

          ✦ Internet Standards Track: This type of RFC represents an Internet
            standard. Standards Track RFCs have one of three maturity levels,
            as described in Table 1-1. An RFC enters circulation with Proposed
            Standard status but may be elevated to Draft Standard status — and,
            ultimately, to Internet Standard status.
                                         TCP/IP Standards and RFCs              285

  Table 1-1        Maturity Levels for Internet Standards Track RFCs
  Maturity Level      Description
  Proposed            Proposed standards are generally stable, have resolved known
  Standard            design choices, are believed to be well understood, have
                      received significant community review, and appear to enjoy
                      enough community interest to be considered valuable.
  Draft Standard      Draft standards are well understood and known to be quite
                      stable. At least two interoperable implementations must exist,
                      developed independently from separate code bases. The
                      specification is believed to be mature and useful.
  Internet            Internet Standards have been fully accepted by the Internet
  Standard            community as highly mature and useful standards.


 ✦ Experimental specifications: These are a result of research or development
   efforts. They’re not intended to be standards, but the information they
   contain may be of use to the Internet community.
 ✦ Informational specifications: These simply provide general information
   for the Internet community.
 ✦ Historic specifications: These RFCs have been superceded by a more
   recent RFC and are thus considered obsolete.
 ✦ Best Current Practice (BCP): RFCs are documents that summarize the
   consensus of the Internet community’s opinion on the best way to
   perform an operation or procedure. BCPs are guidelines, not standards.

Table 1-2 summarizes the RFCs that apply to the key Internet standards
described in this book.



  Table 1-2               RFCs for Key Internet Standards                                  Book IV
  RFC         Date                   Description                                          Chapter 1

  768         August 1980            User Datagram Protocol (UDP)                            Introduction to TCP/
                                                                                              IP and the Internet

  791         September 1981         Internet Protocol (IP)
  792         September 1981         Internet Control Message Protocol (ICMP)
  793         September 1981         Transmission Control Protocol (TCP)
  826         November 1982          Ethernet Address Resolution Protocol (ARP)
                                                                            (continued)
286   The TCP/IP Protocol Framework


           Table 1-2 (continued)
           RFC        Date                Description
           950        August 1985         Internet Standard Subnetting Procedure
           959        October 1985        File Transfer Protocol (FTP)
           1034       November 1987       Domain Names — Concepts and Facilities
                                          (DNS)
           1035       November 1987       Domain Names — Implementation and
                                          Specification (DNS)
           1939       May 1996            Post Office Protocol Version 3 (POP3)
           2131       March 1997          Dynamic Host Configuration Protocol (DHCP)
           2236       November 1997       Internet Group Management Protocol (IGMP)
                                          (Updates RFC 1112)
           2616       June 1999           Hypertext Transfer Protocol — HTTP/1.1
           2821       April 2001          Simple Mail Transfer Protocol (SMTP)


         My favorite RFC is 1149, an experimental specification for the “Transmission
         of IP datagrams on avian carriers.” The specification calls for IP datagrams
         to be written in hexadecimal on scrolls of paper and secured to “avian
         carriers” with duct tape. (Not surprisingly, it’s dated 1 April, 1990. Similar
         RFCs are frequently submitted on April 1.)



The TCP/IP Protocol Framework
         Like the seven-layer OSI Reference Model, TCP/IP protocols are based on
         a layered framework. TCP/IP has four layers, as shown in Figure 1-1. These
         layers are described in the following sections.


         Network Interface layer
         The lowest level of the TCP/IP architecture is the Network Interface layer.
         It corresponds to the OSI Physical and Data Link layers. You can use many
         different TCP/IP protocols at the Network Interface layer, including Ethernet
         and Token Ring for LANs and protocols such as X.25, Frame Relay, and ATM
         for wide area networks (WANs).

         The Network Interface layer is assumed to be unreliable.
                                              The TCP/IP Protocol Framework                 287

                  TCP/IP Layers                          TCP/IP Protocols


                 Application Layer   HTTP          FTP        Telnet        SMTP       DNS



                  Transport Layer                TCP                          UDP


Figure 1-1:       Network Layer             IP                ARP           ICMP        IGMP
The four
layers of
the TCP/IP      Network Interface                                             Other Link-Layer
                                        Ethernet           Token Ring
framework.           Layer                                                       Protocols




              Network layer
              The Network layer is where data is addressed, packaged, and routed among
              networks. Several important Internet protocols operate at the Network layer:

               ✦ Internet Protocol (IP): A routable protocol that uses IP addresses to
                 deliver packets to network devices. IP is an intentionally unreliable
                 protocol, so it doesn’t guarantee delivery of information.
               ✦ Address Resolution Protocol (ARP): Resolves IP addresses to hardware
                 MAC addresses, which uniquely identify hardware devices.
               ✦ Internet Control Message Protocol (ICMP): Sends and receives diagnostic
                 messages. ICMP is the basis of the ubiquitous ping command.
               ✦ Internet Group Management Protocol (IGMP): Used to multicast
                 messages to multiple IP addresses at once.

                                                                                                   Book IV
              Transport layer                                                                     Chapter 1
              The Transport layer is where sessions are established and data packets are             Introduction to TCP/
              exchanged between hosts. Two core protocols are found at this layer:
                                                                                                      IP and the Internet



               ✦ Transmission Control Protocol (TCP): Provides reliable connection-
                 oriented transmission between two hosts. TCP establishes a session
                 between hosts, and then ensures delivery of packets between the hosts.
               ✦ User Datagram Protocol (UDP): Provides connectionless, unreliable,
                 one-to-one or one-to-many delivery.
288   The TCP/IP Protocol Framework


         Application layer
         The Application layer of the TCP/IP model corresponds to the Session,
         Presentation, and Application layers of the OSI Reference Model. A few of the
         most popular Application layer protocols are

          ✦ HyperText Transfer Protocol (HTTP): The core protocol of the World
            Wide Web
          ✦ File Transfer Protocol (FTP): A protocol that enables a client to send
            and receive complete files from a server
          ✦ Telnet: The protocol that lets you connect to another computer on the
            Internet in a terminal emulation mode
          ✦ Simple Mail Transfer Protocol (SMTP): One of several key protocols
            that are used to provide e-mail services
          ✦ Domain Name System (DNS): The protocol that allows you to refer to
            other host computers by using names rather than numbers
      Chapter 2: Understanding
      IP Addresses
      In This Chapter
      ✓ Delving into the binary system
      ✓ Digging into IP addresses
      ✓ Finding out how subnetting works
      ✓ Looking at network address translation




      O    ne of the most basic components of TCP/IP is IP addressing. Every
           device on a TCP/IP network must have a unique IP address. In this
      chapter, I describe the ins and outs of these IP addresses. Enjoy!



Understanding Binary
      Before you can understand the details of how IP addressing works, you need
      to understand how the binary numbering system works because binary is
      the basis of IP addressing. If you already understand binary, please skip to
      the section, “Introducing IP Addresses.” I don’t want to bore you with stuff
      that’s too basic.


      Counting by ones
      Binary is a counting system that uses only two numerals: 0 and 1. In the
      decimal system (with which most people are accustomed), you use 10
      numerals: 0–9. In an ordinary decimal number — such as 3,482 — the rightmost
      digit represents ones; the next digit to the left, tens; the next, hundreds; the
      next, thousands; and so on. These digits represent powers of ten: first 100
      (which is 1); next, 101 (10); then 102 (100); then 103 (1,000); and so on.

      In binary, you have only two numerals rather than ten, which is why binary
      numbers look somewhat monotonous, as in 110011, 101111, and 100001.

      The positions in a binary number (called bits rather than digits) represent
      powers of two rather than powers of ten: 1, 2, 4, 8, 16, 32, and so on. To
      figure the decimal value of a binary number, you multiply each bit by its
      corresponding power of two and then add the results. The decimal value of
      binary 10111, for example, is calculated as follows:
290   Understanding Binary


             1   ×   20   =   1   × 1    =   1
         +   1   ×   21   =   1   × 2    =   2
         +   1   ×   22   =   1   × 4    =   4
         +   0   ×   23   =   0   × 8    =   0
         +   1   ×   24   =   1   × 16   = _16
                                                 23

         Fortunately, converting a number between binary and decimal is something
         a computer is good at — so good, in fact, that you’re unlikely ever to need
         to do any conversions yourself. The point of learning binary is not to be able
         to look at a number such as 1110110110110 and say instantly, “Ah! Decimal
         7,606!” (If you could do that, Barbara Walters would probably interview you,
         and they would even make a movie about you — starring Dustin Hoffman.)

         Instead, the point is to have a basic understanding of how computers store
         information and — most important — to understand how the binary counting
         system works, which I describe in the following section.

         Here are some of the more interesting characteristics of binary and how the
         system is similar to and differs from the decimal system:

          ✦ In decimal, the number of decimal places allotted for a number
            determines how large the number can be. If you allot six digits, for
            example, the largest number possible is 999,999. Because 0 is itself a
            number, however, a six-digit number can have any of 1 million different
            values.
                 Similarly, the number of bits allotted for a binary number determines
                 how large that number can be. If you allot eight bits, the largest value
                 that number can store is 11111111, which happens to be 255 in decimal.
          ✦ To quickly figure how many different values you can store in a binary
            number of a given length, use the number of bits as an exponent
            of two. An eight-bit binary number, for example, can hold 28 values.
            Because 28 is 256, an eight-bit number can have any of 256 different
            values. This is why a byte — eight bits — can have 256 different values.
          ✦ This “powers of two” thing is why computers don’t use nice, even,
            round numbers in measuring such values as memory or disk space.
            A value of 1K, for example, is not an even 1,000 bytes: It’s actually 1,024
            bytes because 1,024 is 210. Similarly, 1MB is not an even 1,000,000 bytes
            but instead 1,048,576 bytes, which happens to be 220.
                 One basic test of computer nerddom is knowing your powers of two
                 because they play such an important role in binary numbers. Just for
                 the fun of it, but not because you really need to know, Table 2-1 lists the
                 powers of two up to 32.
                 Table 2-1 also shows the common shorthand notation for various
                 powers of two. The abbreviation K represents 210 (1,024). The M in
                 MB stands for 220, or 1,024K, and the G in GB represents 230, which is
                                               Understanding Binary         291

       1,024MB. These shorthand notations don’t have anything to do with
       TCP/IP, but they’re commonly used for measuring computer disk and
       memory capacities, so I thought I’d throw them in at no charge because
       the table had extra room.



  Table 2-1                          Powers of Two
  Power       Bytes     Kilobytes      Power             Bytes            K, MB,
                                                                          or GB
  21               2           217       131,072                            128K
   2
  2                4           218       262,144                            256K
   3                            19
  2                8           2         524,288                            512K
   4                            20
  2               16           2        1,048,576                   1MB
  25              32           221      2,097,152                   2MB
   6                            22
  2               64           2        4,194,304                   4MB
   7                            23
  2              128           2        8,388,608                   8MB
   8                            24
  2              256           2       16,777,216                  16MB
  29             512           225     33,554,432                  32MB
   10                                               26
  2             1,024          1K               2          67,108,864       64MB
   11                                               27
  2             2,048          2K               2         134,217,728       128MB
  212           4,096          4K               228       268,435,456       256MB
   13                                               29
  2             8,192          8K               2         536,870,912       512MB
   14                                               30
  2            16,384         16K               2        1,073,741,824        1GB
   15                                               31
  2            32,768         32K               2        2,147,483,648        2GB
  216          65,536         64K               232      4,294,967,296        4GB


                                                                                     Book IV
Doing the logic thing                                                               Chapter 2
One of the great things about binary is that it’s very efficient at handling
special operations: namely, logical operations. Four basic logical operations
                                                                                       Understanding IP
exist although additional operations are derived from the basic four operations.
                                                                                         Addresses



Three of the operations — AND, OR, and XOR — compare two binary digits
(bits). The fourth (NOT) works on just a single bit.

The following list summarizes the basic logical operations:

 ✦ AND: An AND operation compares two binary values. If both values are
   1, the result of the AND operation is 1. If one or both of the values are 0,
   the result is 0.
292   Understanding Binary


          ✦ OR: An OR operation compares two binary values. If at least one of the
            values is 1, the result of the OR operation is 1. If both values are 0, the
            result is 0.
          ✦ XOR: An XOR operation compares two binary values. If exactly one of
            them is 1, the result is 1. If both values are 0 or if both values are 1, the
            result is 0.
          ✦ NOT: The NOT operation doesn’t compare two values. Instead, it simply
            changes the value of a single binary value. If the original value is 1, NOT
            returns 0. If the original value is 0, NOT returns 1.

         Table 2-2 summarizes how AND, OR, and XOR work.



           Table 2-2             Logical Operations for Binary Values
           First Value      Second Value        AND             OR             XOR
           0                0                   0               0              0
           0                1                   0               1              1
           1                0                   0               1              1
           1                1                   1               1              0


         Logical operations are applied to binary numbers that have more than one
         binary digit by applying the operation one bit at a time. The easiest way to
         do this manually is to line the two binary numbers on top of one another and
         then write the result of the operation beneath each binary digit. The following
         example shows how you would calculate 10010100 AND 11011101:

             10010100
         AND 11011101
             10010100

         As you can see, the result is 10010100.


         Working with the binary Windows Calculator
         The Calculator program that comes with all versions of Windows has a
         special Scientific mode that many users don’t know about. When you flip the
         Calculator into this mode, you can do instant binary and decimal conversions,
         which can occasionally come in handy when you’re working with IP addresses.

         To use the Windows Calculator in Scientific mode, launch the Calculator
         by choosing Start➪All Programs➪Accessories➪Calculator. Then, choose
         the View➪Scientific command from the Calculator menu. The Calculator
         changes to a fancy scientific model — the kind I paid $200 for when I was in
         college. All kinds of buttons appear, as shown in Figure 2-1.
                                                       Introducing IP Addresses         293




Figure 2-1:
The free
Windows
scientific
Calculator.



              You can select the Bin and Dec radio buttons to convert values between
              decimal and binary. For example, to find the binary equivalent of decimal
              155, enter 155 and then select the Bin radio button. The value in the display
              changes to 10011011.

              Here are a few other things to note about the Scientific mode of the
              Calculator:

               ✦ Although you can convert decimal values to binary values with the
                 scientific Calculator, the Calculator can’t handle the dotted-decimal
                 IP address format that’s described later in this chapter. To convert a
                 dotted-decimal address to binary, just convert each octet separately.
                 For example, to convert 172.65.48.120 to binary, first convert 172; then
                 convert 65; then convert 48; and finally, convert 120.
               ✦ The scientific Calculator has several features that are designed specifically
                 for binary calculations, such as AND, XOR, NOT, NOR, and so on.
               ✦ The scientific Calculator can also handle hexadecimal conversions.
                 Hexadecimal doesn’t come into play when dealing with IP addresses, but
                 it is used for other types of binary numbers, so this feature sometimes
                 proves to be useful.                                                             Book IV
                                                                                                 Chapter 2
               ✦ Windows 7 does the scientific Calculator one step better by providing
                 a Programmer mode which has even more features for working with                    Understanding IP
                 binary numbers.
                                                                                                      Addresses




Introducing IP Addresses
              An IP address is a number that uniquely identifies every host on an IP network.
              IP addresses operate at the Network layer of the TCP/IP protocol stack, so
              they are independent of lower-level Data Link layer MAC addresses, such as
              Ethernet MAC addresses.
294   Introducing IP Addresses


         IP addresses are 32-bit binary numbers, which means that theoretically,
         a maximum of something in the neighborhood of 4 billion unique host
         addresses can exist throughout the Internet. You’d think that would be
         enough, but TCP/IP places certain restrictions on how IP addresses are
         allocated. These restrictions severely limit the total number of usable IP
         addresses. Many experts predict that we will run out of IP addresses as soon
         as next year. However, new techniques for working with IP addresses have
         helped to alleviate this problem, and a standard for 128-bit IP addresses has
         been adopted, though it still is not yet in widespread use.


         Networks and hosts
         IP stands for Internet protocol, and its primary purpose is to enable
         communications between networks. As a result, a 32-bit IP address actually
         consists of two parts:

          ✦ The network ID (or network address): Identifies the network on which a
            host computer can be found
          ✦ The host ID (or host address): Identifies a specific device on the network
            indicated by the network ID

         Most of the complexity of working with IP addresses has to do with figuring
         out which part of the complete 32-bit IP address is the network ID and which
         part is the host ID, as described in the following sections.

         As I describe the details of how host IDs are assigned, you may notice that
         two host addresses seem to be unaccounted for. For example, the Class C
         addressing scheme, which uses eight bits for the host ID, allows only 254
         hosts — not the 256 hosts you’d expect. That’s because host 0 (the host ID
         is all zeros) is always reserved to represent the network itself. The host ID
         can’t be 255 (the host ID is all ones) because that host ID is reserved for use
         as a broadcast request that’s intended for all hosts on the network.


         The dotted-decimal dance
         IP addresses are usually represented in a format known as dotted-decimal
         notation. In dotted-decimal notation, each group of eight bits — an octet — is
         represented by its decimal equivalent. For example, consider the following
         binary IP address:

         11000000101010001000100000011100

         To convert this value to dotted-decimal notation, first divide it into four
         octets, as follows:

         11000000 10101000 10001000 00011100
                                                           Classifying IP Addresses            295

              Then, convert each of the octets to its decimal equivalent:

              11000000 10101000 10001000 00011100
              192      168      136      28

              Then, use periods to separate the four decimal numbers, like this:

              192.168.136.28

              This is the format in which you’ll usually see IP addresses represented.

              Figure 2-2 shows how the 32 bits of an IP address are broken down into four
              octets of eight bits each. As you can see, the four octets of an IP address are
              often referred to as w, x, y, and z.



                             Network ID                          Host ID


               Class A   0



                                      Network ID                           Host ID


               Class B   1 0




Figure 2-2:                                   Network ID                             Host ID
Octets and
dotted-
decimal        Class C   1 1 0
notation.                                                                                             Book IV
                                                                                                     Chapter 2
                                                                                                        Understanding IP

Classifying IP Addresses
                                                                                                          Addresses




              When the original designers of the IP protocol created the IP addressing
              scheme, they could have assigned an arbitrary number of IP address bits
              for the network ID. The remaining bits would then be used for the host ID.
              For example, suppose that the designers decided that half of the address
              (16 bits) would be used for the network, and the remaining 16 bits would be
              used for the host ID. The result of that scheme would be that the Internet
              could have a total of 65,536 networks, and each of those networks could
              have 65,536 hosts.
296     Classifying IP Addresses




                                   What about IPv6?
  Most of the current Internet is based on version     even a thousand-fold or even a million-fold.
  4 of the Internet Protocol, also known as IPv4.      Just for the fun of it, here is the number of
  IPv4 has served the Internet well for more than      unique Internet addresses provided by IPv6:
  20 years. However, the growth of the Internet
                                                       340,282,366,920,938,463,463,374,607,431,768,21
  has put a lot of pressure on IPv4’s limited 32-bit
                                                       1,456
  address space. This chapter describes how
  IPv4 has evolved to make the best possible           This number is so large it defies understanding.
  use of 32-bit addresses. Eventually, though, all     If the IANA had been around at the creation
  the addresses will be assigned, and the IPv4         of the universe and started handing out IPv6
  address space will be filled to capacity. When       addresses at a rate of one per millisecond —
  that happens, the Internet will have to migrate      that is, 1,000 addresses every second —
  to the next version of IP, known as IPv6.            it would now, 15 billion years later, have not
                                                       yet allocated even 1 percent of the available
  IPv6 is also called IP next generation, or IPng,
                                                       addresses.
  in honor of the favorite television show of most
  Internet gurus, Star Trek: The Next Generation.      The transition from IPv4 to IPv6 has been a
                                                       slow one. IPv6 is available on all new comput-
  IPv6 offers several advantages over IPv4,
                                                       ers and has been supported on Windows since
  but the most important is that it uses 128 bits
                                                       Windows XP Service Pack 1 (released in 2002).
  for Internet addresses instead of 32 bits. The
                                                       However, most Internet service providers
  number of host addresses possible with 128
                                                       (ISPs) still base their service on IPv4. Thus, the
  bits is a number so large that it would have
                                                       Internet will continue to be driven by IPv4 for at
  made Carl Sagan proud. It doesn’t just double
                                                       least a few more years.
  or triple the number of available addresses, or



             In the early days of the Internet, this scheme probably seemed like several
             orders of magnitude more than would ever be needed. However, the IP
             designers realized from the start that few networks would actually have tens
             of thousands of hosts. Suppose that a network of 1,000 computers joins the
             Internet and is assigned one of these hypothetical network IDs. Because that
             network will use only 1,000 of its 65,536 host addresses, more than 64,000 IP
             addresses would be wasted.

             As a solution to this problem, the idea of IP address classes was introduced.
             The IP protocol defines five different address classes: A, B, C, D, and E. Each
             of the first three classes, A–C, uses a different size for the network ID and
             host ID portion of the address. Class D is for a special type of address called
             a multicast address. Class E is an experimental address class that isn’t used.

             The first four bits of the IP address are used to determine into which class a
             particular address fits, as follows:

              ✦ If the first bit is zero, the address is a Class A address.
                                         Classifying IP Addresses           297

 ✦ If the first bit is one and if the second bit is zero, the address is a Class
   B address.
 ✦ If the first two bits are both one and if the third bit is zero, the address
   is a Class C address.
 ✦ If the first three bits are all one and if the fourth bit is zero, the
   address is a Class D address.
 ✦ If the first four bits are all one, the address is a Class E address.

Because Class D and E addresses are reserved for special purposes, I focus
the rest of the discussion here on Class A, B, and C addresses. Table 2-3
summarizes the details of each address class.



 Table 2-3                      IP Address Classes
 Class   Address Number       Starting   Length of    Number of     Hosts
         Range                Bits       Network ID   Networks
 A       1–126.x.y.z                0             8         126     16,777,214
 B       128–191.x.y.z             10            16      16,384         65,534
 C       192–223.x.y.z            110            24    2,097,152            254



Class A addresses
Class A addresses are designed for very large networks. In a Class A address,
the first octet of the address is the network ID, and the remaining three
octets are the host ID. Because only eight bits are allocated to the network
ID and the first of these bits is used to indicate that the address is a Class A
address, only 126 Class A networks can exist in the entire Internet. However,
each Class A network can accommodate more than 16 million hosts.

Only about 40 Class A addresses are actually assigned to companies or               Book IV
organizations. The rest are either reserved for use by the Internet Assigned       Chapter 2
Numbers Authority (IANA) or are assigned to organizations that manage IP
assignments for geographic regions such as Europe, Asia, and Latin America.
                                                                                      Understanding IP
                                                                                        Addresses



Just for fun, Table 2-4 lists some of the better-known Class A networks. You’ll
probably recognize many of them. In case you’re interested, you can find a
complete list of all the Class A address assignments at

www.iana.org/assignments/ipv4-address-space

You may have noticed in Table 2-3 that Class A addresses end with
126.x.y.z, and Class B addresses begin with 128.x.y.z. What happened
to 127.x.y.z? This special range of addresses is reserved for loopback
testing, so these addresses aren’t assigned to public networks.
298   Classifying IP Addresses



            Table 2-4               Some Well-Known Class A Networks
           Net      Description                   Net   Description
           3        General Electric Company      32    Norsk
                                                        Informasjonsteknology
           4        Bolt Beranek and Newman       33    DLA Systems Automation
                    Inc.                                Center
           6        Army Information Systems      35    MERIT Computer Network
                    Center
           8        Bolt Beranek and Newman       38    Performance Systems
                    Inc.                                International
           9        IBM                           40    Eli Lilly and Company
           11       DoD Intel Information         43    Japan Inet
                    Systems
           12       AT&T Bell Laboratories        44    Amateur Radio Digital
                                                        Communications
           13       Xerox Corporation             45    Interop Show Network
           15       Hewlett-Packard Company       46    Bolt Beranek and Newman
                                                        Inc.
           16       Digital Equipment             47    Bell-Northern Research
                    Corporation
           17       Apple Computer Inc.           48    Prudential Securities Inc.
           18       MIT                           51    Department of Social
                                                        Security of UK
           19       Ford Motor Company            52    E.I. duPont de Nemours and
                                                        Co., Inc.
           20       Computer Sciences             53    Cap Debis CCS (Germany)
                    Corporation
           22       Defense Information           54    Merck and Co., Inc.
                    Systems Agency
           25       Royal Signals and Radar       55    Boeing Computer Services
                    Establishment
           26       Defense Information           56    U.S. Postal Service
                    Systems Agency
           28       Decision Sciences Institute   57    SITA
                    (North)
           29–30    Defense Information
                    Systems Agency
                                                                Subnetting      299

      Class B addresses
      In a Class B address, the first two octets of the IP address are used as the
      network ID, and the second two octets are used as the host ID. Thus, a Class
      B address comes close to my hypothetical scheme of splitting the address
      down the middle, using half for the network ID and half for the host ID. It
      isn’t identical to this scheme, however, because the first two bits of the first
      octet are required to be 10, in order to indicate that the address is a Class
      B address. As a result, a total of 16,384 Class B networks can exist. All Class
      B addresses fall within the range 128.x.y.z to 191.x.y.z. Each Class B
      address can accommodate more than 65,000 hosts.

      The problem with Class B networks is that even though they are much
      smaller than Class A networks, they still allocate far too many host IDs. Very
      few networks have tens of thousands of hosts. Thus, careless assignment
      of Class B addresses can lead to a large percentage of the available host
      addresses being wasted on organizations that don’t need them.


      Class C addresses
      In a Class C address, the first three octets are used for the network ID, and
      the fourth octet is used for the host ID. With only eight bits for the host ID,
      each Class C network can accommodate only 254 hosts. However, with 24
      network ID bits, Class C addresses allow for more than 2 million networks.

      The problem with Class C networks is that they’re too small. Although few
      organizations need the tens of thousands of host addresses provided by a
      Class B address, many organizations need more than a few hundred. The
      large discrepancy between Class B networks and Class C networks is what
      led to the development of subnetting, which I describe in the next section.



Subnetting
      Subnetting is a technique that lets network administrators use the 32 bits           Book IV
      available in an IP address more efficiently by creating networks that aren’t        Chapter 2
      limited to the scales provided by Class A, B, and C IP addresses. With
      subnetting, you can create networks with more realistic host limits.
                                                                                             Understanding IP
                                                                                               Addresses



      Subnetting provides a more flexible way to designate which portion of an IP
      address represents the network ID and which portion represents the host ID.
      With standard IP address classes, only three possible network ID sizes exist:
      8 bits for Class A, 16 bits for Class B, and 24 bits for Class C. Subnetting lets
      you select an arbitrary number of bits to use for the network ID.
300   Subnetting


         Two reasons compel people to use subnetting. The first is to allocate the
         limited IP address space more efficiently. If the Internet were limited to Class
         A, B, or C addresses, every network would be allocated 254, 64 thousand, or
         16 million IP addresses for host devices. Although many networks with more
         than 254 devices exist, few (if any) exist with 64 thousand, let alone 16 million.
         Unfortunately, any network with more than 254 devices would need a Class
         B allocation and probably waste tens of thousands of IP addresses.

         The second reason for subnetting is that even if a single organization has
         thousands of network devices, operating all those devices with the same
         network ID would slow the network to a crawl. The way TCP/IP works
         dictates that all the computers with the same network ID must be on the
         same physical network. The physical network comprises a single broadcast
         domain, which means that a single network medium must carry all the traffic
         for the network. For performance reasons, networks are usually segmented
         into broadcast domains that are smaller than even Class C addresses provide.


         Subnets
         A subnet is a network that falls within a Class A, B, or C network. Subnets are
         created by using one or more of the Class A, B, or C host bits to extend the
         network ID. Thus, instead of the standard 8-, 16-, or 24-bit network ID, subnets
         can have network IDs of any length.

         Figure 2-3 shows an example of a network before and after subnetting has
         been applied. In the unsubnetted network, the network has been assigned
         the Class B address 144.28.0.0. All the devices on this network must
         share the same broadcast domain.

         In the second network, the first four bits of the host ID are used to divide the
         network into two small networks, identified as subnets 16 and 32. To the
         outside world (that is, on the other side of the router), these two networks
         still appear to be a single network identified as 144.28.0.0. For example,
         the outside world considers the device at 144.28.16.22 to belong to the
         144.28.0.0 network. As a result, a packet sent to this device will be deliv-
         ered to the router at 144.28.0.0. The router then considers the subnet
         portion of the host ID to decide whether to route the packet to subnet 16 or
         subnet 32.


         Subnet masks
         For subnetting to work, the router must be told which portion of the host
         ID should be used for the subnet network ID. This little sleight of hand is
         accomplished by using another 32-bit number, known as a subnet mask.
         Those IP address bits that represent the network ID are represented by a 1
         in the mask, and those bits that represent the host ID appear as a 0 in the
         mask. As a result, a subnet mask always has a consecutive string of ones on
         the left, followed by a string of zeros.
                                                                            Subnetting          301

                  Before subnetting



                     The Internet        144.28.0.0
                                                                                   144.28.0.0
                                                           Router




                   After subnetting

                                                                                  144.28.16.0
Figure 2-3:
A network                                144.28.0.0
                     The Internet
before
and after                                                  Router                 144.28.32.0
subnetting.



              For example, the subnet mask for the subnet shown in Figure 2-3, where the
              network ID consists of the 16-bit network ID plus an additional 4-bit subnet
              ID, would look like this:

              11111111 11111111 11110000 00000000

              In other words, the first 20 bits are ones, and the remaining 12 bits are zeros.
              Thus, the complete network ID is 20 bits in length, and the actual host ID
              portion of the subnetted address is 12 bits in length.

              To determine the network ID of an IP address, the router must have both the
              IP address and the subnet mask. The router then performs a bitwise operation
              called a logical AND on the IP address in order to extract the network ID. To              Book IV
              perform a logical AND, each bit in the IP address is compared with the                    Chapter 2
              corresponding bit in the subnet mask. If both bits are 1, the resulting bit in
              the network ID is set to 1. If either of the bits are 0, the resulting bit is set to 0.      Understanding IP
                                                                                                             Addresses


              For example, here’s how the network address is extracted from an IP
              address using the 20-bit subnet mask from the previous example:

                              144 .     28 .     16 .    17
              IP address: 10010000 00011100 00010000 00010001
              Subnet mask: 11111111 11111111 11110000 00000000
              Network ID: 10010000 00011100 00010000 00000000
                              144 .     28 .     16 .     0

              Thus, the network ID for this subnet is 144.28.16.0.
302   Subnetting


         The subnet mask itself is usually represented in dotted-decimal notation. As
         a result, the 20-bit subnet mask used in the previous example would be
         represented as 255.255.240.0:

         Subnet mask: 11111111 11111111 11110000 00000000
                         255 .    255 .    240 .    0

         Don’t confuse a subnet mask with an IP address. A subnet mask doesn’t
         represent any device or network on the Internet. It’s just a way of indicating
         which portion of an IP address should be used to determine the network ID.
         (You can spot a subnet mask right away because the first octet is always
         255, and 255 is not a valid first octet for any class of IP address.)


         Network prefix notation
         Because a subnet mask always begins with a consecutive sequence of ones
         to indicate which bits to use for the network ID, you can use a shorthand
         notation — a network prefix — to indicate how many bits of an IP address
         represent the network ID. The network prefix is indicated with a slash
         immediately after the IP address, followed by the number of network ID bits
         to use. For example, the IP address 144.28.16.17 with the subnet mask
         255.255.240.0 can be represented as 144.28.16.17/20 because the
         subnet mask 255.255.240.0 has 20 network ID bits.

         Network prefix notation is also called classless interdomain routing notation
         (CIDR, for short) because it provides a way of indicating which portion of an
         address is the network ID and which is the host ID without relying on standard
         address classes.


         Default subnets
         The default subnet masks are three subnet masks that correspond to the
         standard Class A, B, and C address assignments. These default masks are
         summarized in Table 2-5.



           Table 2-5               The Default Subnet Masks
           Class     Binary                           Dotted-Decimal         Network
                                                                             Prefix
           A         11111111 00000000                255.0.0.0              /8
                     00000000 00000000
           B         11111111 11111111                255.255.0.0            /16
                     00000000 00000000
           C         11111111 11111111                255.255.255.0          /24
                     11111111 00000000
                                                           Subnetting      303

Keep in mind that a subnet mask is not actually required to use one of these
defaults because the IP address class can be determined by examining the
first three bits of the IP address. If the first bit is 0, the address is Class A,
and the subnet mask 255.0.0 is applied. If the first two bits are 10, the
address is Class B, and 255.255.0.0 is used. If the first three bits are 110,
the Class C default mask 255.255.255.0 is used.


The great subnet roundup
You should know about a few additional restrictions that are placed on
subnets and subnet masks. In particular

 ✦ The minimum number of network ID bits is eight. As a result, the first
   octet of a subnet mask is always 255.
 ✦ The maximum number of network ID bits is 30. You have to leave at
   least two bits for the host ID portion of the address to allow for at least
   two hosts. If you use all 32 bits for the network ID, that leaves no bits
   for the host ID. Obviously, that won’t work. Leaving just one bit for the
   host ID won’t work, either, because a host ID of all ones is reserved for a
   broadcast address, and all zeros refers to the network itself. Thus, if you
   use 31 bits for the network ID and leave only 1 for the host ID, host ID
   1 would be used for the broadcast address, and host ID 0 would be the
   network itself, leaving no room for actual hosts. That’s why the maximum
   network ID size is 30 bits.
 ✦ Because the network ID portion of a subnet mask is always composed
   of consecutive bits set to 1, only eight values are possible for each
   octet of a subnet mask: 0, 128, 192, 224, 248, 252, 254, and 255.
 ✦ A subnet address can’t be all zeros or all ones. Thus, the number of
   unique subnet addresses is two less than two raised to the number of
   subnet address bits. For example, with three subnet address bits, six
   unique subnet addresses are possible (23 – 2 = 6). This implies that you
   must have at least two subnet bits. (If a single-bit subnet mask were
   allowed, it would violate the “can’t be all zeros or all ones” rule because
                                                                                      Book IV
   the only two allowed values would be 0 or 1.)                                     Chapter 2


IP block parties
                                                                                        Understanding IP
                                                                                          Addresses


A subnet can be thought of as a range or block of IP addresses that have a
common network ID. For example, the CIDR 192.168.1.0/28 represents
the following block of 14 IP addresses:

192.168.1.1       192.168.1.2        192.168.1.3        192.168.1.4
192.168.1.5       192.168.1.6        192.168.1.7        192.168.1.8
192.168.1.9       192.168.1.10       192.168.1.11       192.168.1.12
192.168.1.13      192.168.1.14
304   Subnetting


         Given an IP address in CIDR notation, it’s useful to be able to determine
         the range of actual IP addresses that the CIDR represents. This matter is
         straightforward when the octet within which the network ID mask ends
         happens to be 0, as in the preceding example. You just determine how many
         host IDs are allowed based on the size of the network ID and count them off.

         However, what if the octet where the network ID mask ends is not 0? For
         example, what are the valid IP addresses for 192.168.1.100 when the
         subnet mask is 255.255.255.240? In that case, the calculation is a little
         harder. The first step is to determine the actual network ID. You can do that
         by converting both the IP address and the subnet mask to binary and then
         extracting the network ID as in this example:

                         192 .    168 .      1 .    100
         IP address: 11000000 10101000 00000001 01100100
         Subnet mask: 11111111 11111111 11111111 11110000
         Network ID: 11000000 10101000 00000001 01100000
                         192 .    168 .      1 .    96

         As a result, the network ID is 192.168.1.96.

         Next, determine the number of allowable hosts in the subnet based on the
         network prefix. You can calculate this by subtracting the last octet of the
         subnet mask from 254. In this case, the number of allowable hosts is 14.

         To determine the first IP address in the block, add 1 to the network ID.
         Thus, the first IP address in my example is 192.168.1.97. To determine
         the last IP address in the block, add the number of hosts to the network
         ID. In my example, the last IP address is 192.168.1.110. As a result, the
         192.168.1.100 with subnet mask 255.255.255.240 designates the
         following block of IP addresses:

         192.168.1.97     192.168.1.98 192.168.1.99            192.168.1.100
         192.168.1.101    192.168.1.102 192.168.1.103          192.168.1.104
         192.168.1.105    192.168.1.106 192.168.1.107          192.168.1.108
         192.168.1.109    192.168.1.110


         Private and public addresses
         Any host with a direct connection to the Internet must have a globally
         unique IP address. However, not all hosts are connected directly to the
         Internet. Some are on networks that aren’t connected to the Internet. Some
         hosts are hidden behind firewalls, so their Internet connection is indirect.

         Several blocks of IP addresses are set aside just for this purpose, for use
         on private networks that are not connected to the Internet or to use on
         networks that are hidden behind a firewall. Three such ranges of addresses
         exist, summarized in Table 2-6. Whenever you create a private TCP/IP network,
         you should use IP addresses from one of these ranges.
                                            Network Address Translation        305

        Table 2-6                    Private Address Spaces
        CIDR                  Subnet Mask         Address Range
        10.0.0.0/8            255.0.0.0           10.0.0.1–10.255.255.254
        172.16.0.0/12         255.255.240.0       172.16.1.1–172.31.255.254
        192.168.0.0/16        255.255.0.0         192.168.0.1–192.168.255.254




Network Address Translation
       Many firewalls use a technique called network address translation (NAT) to
       hide the actual IP address of a host from the outside world. When that’s the
       case, the NAT device must use a globally unique IP to represent the host to
       the Internet. Behind the firewall, though, the host can use any IP address it
       wants. When packets cross the firewall, the NAT device translates the private
       IP address to the public IP address and vice versa.

       One of the benefits of NAT is that it helps to slow down the rate at which the
       IP address space is assigned. That’s because a NAT device can use a single
       public IP address for more than one host. It does so by keeping track of
       outgoing packets so that it can match incoming packets with the correct
       host. To understand how this works, consider the following sequence of steps:

       1. A host whose private address is 192.168.1.100 sends a request to
           216.239.57.99, which happens to be www.google.com. The NAT
           device changes the source IP address of the packet to 208.23.110.22,
           the IP address of the firewall. That way, Google will send its reply back
           to the firewall router. The NAT records that 192.168.1.100 sent a
           request to 216.239.57.99.
       2. Now another host, at address 192.168.1.107, sends a request to
           207.46.134.190, which happens to be www.microsoft.com. The
           NAT device changes the source of this request to 208.23.110.22 so              Book IV
           that Microsoft will reply to the firewall router. The NAT records that        Chapter 2
           192.168.1.107 sent a request to 207.46.134.190.                                  Understanding IP
       3. A few seconds later, the firewall receives a reply from 216.239.57.99.
                                                                                              Addresses


           The destination address in the reply is 208.23.110.22, the address
           of the firewall. To determine to whom to forward the reply, the firewall
           checks its records to see who is waiting for a reply from 216.239.57.99.
           It discovers that 192.168.1.100 is waiting for that reply, so it changes
           the destination address to 192.168.1.100 and sends the packet on.

       Actually, the process is a little more complicated than that, because it’s very
       likely that two or more users may have pending requests from the same
       public IP. In that case, the NAT device uses other techniques to figure out to
       which user each incoming packet should be delivered.
306   Book IV: TCP/IP and the Internet
      Chapter 3: Using DHCP
      In This Chapter
      ✓ Discovering the basics of DHCP
      ✓ Exploring scopes
      ✓ Configuring a DHCP server
      ✓ Setting up a DHCP client




      E    very host on a Transmission Control Protocol/Internet Protocol (TCP/
           IP) network must have a unique IP address. Each host must be properly
      configured so that it knows its IP address. When a new host comes online, it
      must be assigned an IP address that’s within the correct range of addresses
      for the subnet but not already in use. Although you can manually assign IP
      addresses to each computer on your network, that task quickly becomes
      overwhelming if the network has more than a few computers.

      That’s where DHCP — Dynamic Host Configuration Protocol — comes into
      play. DHCP automatically configures the IP address for every host on a
      network, thus assuring that each host has a valid, unique IP address. DHCP
      even automatically reconfigures IP addresses as hosts come and go. As you
      can imagine, DHCP can save a network administrator many hours of tedious
      configuration work.

      In this chapter, you discover the ins and outs of DHCP: what it is, how it
      works, and how to set it up.



Understanding DHCP
      DHCP allows individual computers on a TCP/IP network to obtain their
      configuration information — in particular, their IP address — from a server.
      The DHCP server keeps track of which IP addresses are already assigned so
      that when a computer requests an IP address, the DHCP server offers it an
      IP address that’s not already in use.


      Configuration information provided by DHCP
      Although the primary job of DHCP is to dole out IP addresses and subnet
      masks, DHCP actually provides more configuration information than just the
      IP address to its clients. The additional configuration information are DHCP
      options. The following is a list of some common DHCP options that can be
      configured by the server:
308   Understanding DHCP


          ✦ The router address, also known as the Default Gateway address
          ✦ The expiration time for the configuration information
          ✦ Domain name
          ✦ Domain Name Server (DNS) server address
          ✦ Windows Internet Name Service (WINS) server address


         DHCP servers
         A DHCP server can be a server computer located on the TCP/IP network.
         All modern server operating systems have a built-in DHCP server. To set up
         DHCP on a network server, all you have to do is enable the server’s DHCP
         function and configure its settings. In the upcoming section, “Working with
         a DHCP Server,” I show you how to configure a DHCP server for Windows
         Server 2008. (The procedure for Windows Server 2003 is similar.)

         A server computer running DHCP doesn’t have to be devoted entirely to
         DHCP unless the network is very large. For most networks, a file server can
         share duty as a DHCP server. This is especially true if you provide long
         leases for your IP addresses. (I explain the idea of leases later in this chapter.)

         Many multifunction routers also have built-in DHCP servers. If you don’t
         want to burden one of your network servers with the DHCP function, you
         can enable the router’s built-in DHCP server. An advantage of allowing the
         router to be your network’s DHCP server is that you rarely need to power-down
         a router. In contrast, you occasionally need to restart or power-down a file
         server to perform system maintenance, apply upgrades, or perform
         troubleshooting.

         Most networks require only one DHCP server. Setting up two or more
         servers on the same network requires that you carefully coordinate the IP
         address ranges (known as scopes) for which each server is responsible. If
         you accidentally set up two DHCP servers for the same scope, you may end
         up with duplicate address assignments if the servers attempt to assign the
         same IP address to two different hosts. To prevent this from happening, just
         set up one DHCP server unless your network is so large that one server can’t
         handle the workload.


         How DHCP actually works
         You can configure and use DHCP without knowing the details of how DHCP
         client configuration actually works. However, a basic understanding of the
         process can help you to understand what DHCP is actually doing. Not
         only is this understanding enlightening, but it can also help when you’re
         troubleshooting DHCP problems.
                                            Understanding DHCP           309

The following paragraphs contain a blow-by-blow account of how DHCP
configures TCP/IP hosts. This procedure happens every time you boot up a
host computer. It also happens when you release an IP lease and request a
fresh lease.

1. When a host computer starts up, the DHCP client software sends a
    special broadcast packet, known as a DHCP Discover message.
    This message uses the subnet’s broadcast address (all host ID bits set to
    one) as the destination address and 0.0.0.0 as the source address.
    The client has to specify 0.0.0.0 as the source address because it
    doesn’t yet have an IP address, and it specifies the broadcast address
    as the destination address because it doesn’t know the address of any
    DHCP servers. In effect, the DHCP Discover message is saying, “Hey! I’m
    new here. Are there any DHCP servers out there?”
2. The DHCP server receives the broadcast DHCP Discover message and
    responds by sending a DHCP Offer message.
    The DHCP Offer message includes an IP address that the client can use.
    Like the DHCP Discover message, the DHCP Offer message is sent to the
    broadcast address. This makes sense because the client to which the
    message is being sent doesn’t yet have an IP address and won’t have
    one until it accepts the offer. In effect, the DHCP Offer message is saying,
    “Hello there, whoever you are. Here’s an IP address you can use, if you
    want it. Let me know.”
    What if the client never receives a DHCP Offer message from a DHCP
    server? In that case, the client waits for a few seconds and tries again.
    The client will try four times — at 2, 4, 8, and 16 seconds. If it still
    doesn’t get an offer, it will try again after five minutes.
3. The client receives the DHCP Offer message and sends back a message
    known as a DHCP Request message.
    At this point, the client doesn’t actually own the IP address: It’s simply
    indicating that it’s ready to accept the IP address that was offered by the     Book IV
    server. In effect, the DHCP Request message says, “Yes, that IP address        Chapter 3
    would be good for me. Can I have it, please?”
4. When the server receives the DHCP Request message, it marks the IP
                                                                                         Using DHCP

    address as assigned to the client and broadcasts a DHCP Ack message.
    The DHCP Ack message says, in effect, “Okay, it’s all yours. Here’s the
    rest of the information you need to use it.”
5. When the client receives the DHCP Ack message, it configures its TCP/IP
    stack by using the address it accepted from the server.
310   Understanding Scopes


Understanding Scopes
         A scope is simply a range of IP addresses that a DHCP server is configured
         to distribute. In the simplest case, where a single DHCP server oversees IP
         configuration for an entire subnet, the scope corresponds to the subnet.
         However, if you set up two DHCP servers for a subnet, you can configure
         each with a scope that allocates only one part of the complete subnet range.
         In addition, a single DHCP server can serve more than one scope.

         You must create a scope before you can enable a DHCP server. When you
         create a scope, you can provide it with the following properties:

          ✦ A scope name, which helps you to identify the scope and its purpose
          ✦ A scope description, which lets you provide additional details about the
            scope and its purpose
          ✦ A starting IP address for the scope
          ✦ An ending IP address for the scope
          ✦ A subnet mask for the scope
             You can specify the subnet mask with dotted-decimal notation or with
             network prefix notation.
          ✦ One or more ranges of excluded addresses
             These addresses won’t be assigned to clients. For more information, see
             the section “Feeling excluded?” later in this chapter.
          ✦ One or more reserved addresses
             These are addresses that will always be assigned to particular host
             devices. For more information, see the section “Reservations suggested”
             later in this chapter.
          ✦ The lease duration, which indicates how long the host will be allowed to
            use the IP address
             The client will attempt to renew the lease when half of the lease duration
             has elapsed. For example, if you specify a lease duration of eight days,
             the client will attempt to renew the lease after four days pass. This
             allows the host plenty of time to renew the lease before the address is
             reassigned to some other host.
          ✦ The router address for the subnet
             This value is also known as the Default Gateway address.
          ✦ The domain name and the IP address of the network’s DNS servers
            and WINS servers
                                           Understanding Scopes         311

Feeling excluded?
Everyone feels excluded once in awhile. With a wife, three daughters, and
a female dog, I know how it feels. Sometimes, however, being excluded is a
good thing. In the case of DHCP scopes, exclusions can help you to prevent
IP address conflicts and can enable you to divide the DHCP workload for a
single subnet among two or more DHCP servers.

An exclusion is a range of addresses that are not included in a scope. The
exclusion range falls within the range of the scope’s starting and ending
addresses. In effect, an exclusion range lets you punch a hole in a scope. The
IP addresses that fall within the hole won’t be assigned.

Here are a few reasons for excluding IP addresses from a scope:

 ✦ The computer that runs the DHCP service itself must usually have
   a static IP address assignment. As a result, the address of the DHCP
   server should be listed as an exclusion.
 ✦ Some hosts may not be able to support DHCP. In that case, the host
   will require a static IP address. For example, you may have a really old
   MS-DOS computer that doesn’t have a DHCP client. By excluding its
   IP address from the scope, you can prevent that address from being
   assigned to any other host on the network.


Reservations suggested
In some cases, you may want to assign a particular IP address to a particular
host. One way to do this is to configure the host with a static IP address so
that the host doesn’t use DHCP to obtain its IP configuration. However, here
are two major disadvantages to that approach:

 ✦ TCP/IP configuration supplies more than just the IP address. If you use
   static configuration, you must manually specify the subnet mask, the
   Default Gateway address, the DNS server address, and other configuration
   information required by the host. If this information changes, you have        Book IV
   to change it not only at the DHCP server, but also at each host that you      Chapter 3
   configured statically.
 ✦ You must remember to exclude the static IP address from the DHCP
                                                                                       Using DHCP

   server’s scope. Otherwise, the DHCP server won’t know about the static
   address and may assign it to another host. Then, you’ll have two hosts
   with the same address on your network.

A better way to assign a fixed IP address to a particular host is to create a
DHCP reservation. A reservation simply indicates that whenever a particular
host requests an IP address from the DHCP server, the server should provide
it the address that you specify in the reservation. The host won’t receive the
IP address until the host requests it from the DHCP server, but whenever the
host does request IP configuration, it will always receive the same address.
312    Understanding Scopes




                               What about BootP?
  BootP — Bootstrap Protocol — is an Internet      after an operating system has been loaded,
  protocol that enables diskless workstations      during the configuration of network devices.
  to boot themselves over the Internet or local
                                                   Most DHCP servers can also support BootP. If
  network. Like DHCP, BootP allows a
                                                   your network has diskless workstations, you
  computer to receive an IP address assigned
                                                   can use the DHCP server’s BootP support to
  from a server. However, unlike DHCP, BootP
                                                   boot those computers. At one time, diskless
  also enables the computer to download a boot
                                                   workstations were all the rage because
  image file, which the computer can then use
                                                   network administrators thought they’d be
  to boot itself from. A significant difference
                                                   easier to manage. Users hated them, however.
  between BootP and DHCP is that BootP comes
                                                   Most diskless workstations have now been
  into play before the computer actually loads
                                                   buried in landfills, and BootP isn’t used much.
  an operating system. In contrast, DHCP is used




            To create a reservation, you associate the IP address that you want assigned
            to the host with the host’s MAC address. As a result, you need to get the
            MAC address from the host before you create the reservation. You can get
            the MAC address by running the command ipconfig /all from a command
            prompt. (If that fails because TCP/IP has not yet been configured on the
            computer, you can also get the MAC address [the number that uniquely
            identifies the hardware device] by running the System Information command,
            which is Start➪All Programs➪Accessories➪System Tools➪System Information.)

            If you set up more than one DHCP server, each should be configured to
            serve a different range of IP addresses. Otherwise, the servers might assign
            the same address to two different hosts.


            How long to lease?
            One of the most important decisions that you’ll make when you configure
            a DHCP server is the length of time to specify for the lease duration. The
            default value is eight days, which is appropriate in many cases. However,
            you may encounter situations in which a longer or shorter interval may be
            appropriate:

             ✦ The more stable your network, the longer the lease duration can safely
               exist. If you only periodically add new computers to the network or
               replace existing computers, you can safely increase the lease duration
               past eight days.
             ✦ The more volatile the network, the shorter the lease duration should be.
               For example, a wireless network in a university library is used by students
               who bring their laptop computers into the library to work for a few hours at
               a time. For this network, a duration such as one hour may be appropriate.
                                          Working with a DHCP Server          313

      Don’t configure your network to allow infinite duration leases. Some
      administrators feel that this cuts down the workload for the DHCP server
      on stable networks. However, no network is permanently stable. Whenever
      you find a DHCP server that’s configured with infinite leases, look at the
      active leases. I guarantee you’ll find IP leases assigned to computers that no
      longer exist.



Working with a DHCP Server
      The exact steps that you should follow when configuring and managing a
      DHCP server depend on the network operating system that you’re using. The
      following procedures show you how to work with a DHCP server in Windows
      Server 2008. The procedures for other operating systems are similar.


      Installing and configuring a DHCP server
      To install the DHCP server role on Windows Server 2008, follow these steps:

       1. Choose Start➪Administrative Tools➪Server Manager.
          The Manage Your Server application appears.
       2. Click the Roles link and then click Add a Role.
          The Add Roles Wizard appears.
       3. Click Next to get the wizard started.
          The wizard displays a list of available server roles.
       4. Select DHCP Server from the list of roles and then click Next.
          The wizard displays an explanation of DHCP.
       5. Click Next.
          The wizard displays a list of the server’s network connections that have
          static IP addresses, as shown in Figure 3-1. (In this example, only one       Book IV
          network connection has a static IP address assigned. Most network            Chapter 3
          servers will have at least two.)
       6. Select the static IP addresses you want to use for the DHCP server.
                                                                                             Using DHCP

          Then click Next.
          The wizard asks for the DNS configuration information, as shown in
          Figure 3-2.
       7. Enter the domain name and DNS servers. To enter a DNS server, type
          its address in the IP address text box and then click Add.
          You typically have more than one DNS server.
314      Working with a DHCP Server




Figure 3-1:
Select the
static IP
addresses
to use for
this DHCP
server.




Figure 3-2:
Specify
the DNS
information.



               8. Click Next.
                  The wizard next asks for the WINS configuration information.
               9. (Optional) If you want to enable WINS, enter the WINS server
                  configuration and then click Next.
                  If you don’t want to use WINS, skip this step and just click Next.
                  Either way, the next screen lets you configure scopes.
                                                 Working with a DHCP Server           315

              10. To create a new scope, click the Add Scope button.
                  The wizard asks for a name and description for the new scope, as shown
                  in Figure 3-3.




Figure 3-3:
Creating a
new scope.



              11. Enter the information for the new scope.
                  You must enter the following information:
                   • Scope Name: The name can be anything you want. I suggest that you
                     use a generic name such as Office or your company name unless
                     you’re creating two or more scopes. Then, the names should indicate
                     the function of each scope.
                   • Scope Starting IP Address: This is the lowest IP address that will be
                     issued for this scope.
                   • Scope Ending IP Address: This is the highest IP address that will be
                     issued for this scope.
                   • Subnet Mask: This is the subnet mask issued for IP addresses in this
                     scope.                                                                     Book IV
                                                                                               Chapter 3
                   • Default Gateway: This is the default gateway address that will be
                     used for this scope. This is usually the address of your router.                Using DHCP

                   • Subnet type: Choose Wired or Wireless. The difference is how long
                     the IP address will be valid. For wired networks, the addresses will
                     be valid for six days. For wireless networks, the addresses will expire
                     in eight hours.
              12. Select the Activate This Scope check box and then Click OK.
                  The scope is created, as shown in Figure 3-4.
316     Working with a DHCP Server




Figure 3-4:
The scope is
created.



               13. If you want to create additional scopes, repeat Steps 10–12.
                   You can create as many scopes as you want for your DHCP server.
               14. When you finish creating scopes, click Next.
                   The wizard asks whether you want to enable stateless mode, which is
                   used for IPv6. I recommend disabling this mode unless dealing with IPv6
                   clients is important to your network.
               15. Click Next.
                   The wizard asks for the credentials to use when creating this DHCP
                   server. The default is to use your current login credentials.
               16. Click Next.
                   The wizard displays a confirmation screen that summarizes the settings
                   you’ve entered for the DHCP server.
               17. Click Install.
                   The DHCP server is created. This might take a few minutes. When the
                   server is finished, a final results page is displayed to confirm that the
                   server was properly installed.
               18. Click Close.
                   You’re done!


               Managing a DHCP server
               You can bring up the DHCP management console by choosing Start➪
               Administrative Tools➪DHCP or by clicking Manage This DHCP Server from
               the Manage Your Server application. Either way, the DHCP management
               console appears, as shown in Figure 3-5.
                                                Working with a DHCP Server          317




Figure 3-5:
The DHCP
management
console.



              From the DHCP console, you have complete control over the DHCP server’s
              configuration and operation. The following list summarizes some of the
              things that you can do from the DHCP console:

              ✦ You can authorize the DHCP server, which allows it to begin assigning
                client IP addresses. To authorize a server, select the server, choose
                Action➪Manage Authorized Servers, and then click Authorize.
              ✦ To add another scope, right-click the server in the tree and choose
                the New Scope command from the menu that appears. This brings
                up the New Scope Wizard. You can follow Steps 5–18 in the preceding
                section to complete the wizard.
              ✦ To activate or deactivate a scope, right-click the scope in the tree and
                then choose the Activate or Deactivate command.
              ✦ To change scope settings, right-click the scope and choose the
                Properties command. This brings up the Scope Properties dialog box, as
                shown in Figure 3-6. From this dialog box, you can change the scope’s         Book IV
                start and end IP addresses, subnet mask, and DNS configuration.              Chapter 3
              ✦ To change the scope exclusions, click Address Pool under the scope in
                the tree. This lists each range of addresses that’s included in the scope.
                                                                                                   Using DHCP

                You can add or delete a range by right-clicking the range and choos-
                ing the Delete command from the menu that appears. You can also add
                a new exclusion range by right-clicking Address Pool in the tree and
                choosing Add New Exclusion from the contextual menu that appears.
              ✦ To view or change reservations, click Reservations in the tree.
              ✦ To view a list of assigned addresses, click Address Leases in the tree.
318       How to Configure a Windows DHCP Client




Figure 3-6:
The Scope
Properties
dialog box.




How to Configure a Windows DHCP Client
                Configuring a Windows client for DHCP is easy. The DHCP client is
                automatically included when you install the TCP/IP protocol, so all you have
                to do is configure TCP/IP to use DHCP. To do this, bring up the Network
                Properties dialog box by choosing Network or Network Connections in the
                Control Panel (depending on which version of Windows the client is running).
                Then, select the TCP/IP protocol and click the Properties button. This brings
                up the TCP/IP Properties dialog box, as shown in Figure 3-7. To configure the
                computer to use DHCP, select the Obtain an IP Address Automatically option
                and the Obtain DNS Server Address Automatically option.




Figure 3-7:
Configuring
a Windows
client to use
DHCP.
                    How to Configure a Windows DHCP Client              319

Automatic Private IP Addressing
If a Windows computer is configured to use DHCP but the computer can’t
obtain an IP address from a DHCP server, the computer automatically
assigns itself a private address by using a feature called Automatic Private IP
Addressing (APIPA). APIPA assigns a private address from the 169.254.x.x
range and uses a special algorithm to ensure that the address is unique on
the network. As soon as the DHCP server becomes available, the computer
requests a new address, so the APIPA address is used only while the DHCP
server is unavailable.


Renewing and releasing leases
Normally, a DHCP client attempts to renew its lease when the lease is halfway
to the point of being expired. For example, if a client obtains an eight-day
lease, it attempts to renew the lease after four days. However, you can renew
a lease sooner by issuing the ipconfig /renew command at a command
prompt. You may want to do this if you changed the scope’s configuration or
if the client’s IP configuration isn’t working correctly.

You can also release a DHCP lease by issuing the ipconfig /release
command at a command prompt. When you release a lease, the client
computer no longer has a valid IP address. This is shown in the output from
the ipconfig /release command:

C:\>ipconfig /release
Windows IP Configuration
Ethernet adapter Local Area        Connection:
        Connection-specific        DNS Suffix      .   :
        IP Address. . . . .        . . . . . .     .   : 0.0.0.0
        Subnet Mask . . . .        . . . . . .     .   : 0.0.0.0
        Default Gateway . .        . . . . . .     .   :

Here, you can see that the IP address and subnet masks are set to 0.0.0.0
and that the Default Gateway address is blank. When you release an IP lease,
you can’t communicate with the network by using TCP/IP until you issue an          Book IV
ipconfig /renew command to renew the IP configuration or restart the              Chapter 3
computer.                                                                               Using DHCP
320   Book IV: TCP/IP and the Internet
      Chapter 4: Using DNS
      In This Chapter
      ✓ Discovering the basics of DNS
      ✓ Exploring zones
      ✓ Examining resource records
      ✓ Configuring a DNS server
      ✓ Setting up a DNS client




      D    omain Name Server — DNS — is the TCP/IP facility that lets you use
           names rather than numbers to refer to host computers. Without DNS,
      you’d buy books from 207.171.166.252 instead of from www.amazon.
      com, you’d sell your used furniture at 66.211.160.87 instead of on
      www.ebay.com, and you’d search the Web at 74.125.19.147 instead of
      at www.google.com.

      Understanding how DNS works and how to set up a DNS server is crucial
      to setting up and administering a Transmission Control Protocol/Internet
      Protocol (TCP/IP) network. This chapter introduces you to the basics of
      DNS, including how the DNS naming system works and how to set up a DNS
      server.

      If you want to review the complete official specifications for DNS, look up
      RFC 1034 and 1035 at www.ietf.org/rfc/rfc1034.txt and www.ietf.
      org/rfc/rfc1035.txt, respectively.



Understanding DNS Names
      DNS is a name service that provides a standardized system for providing
      names to identify TCP/IP hosts as well as a way to look up the IP address
      of a host, given the host’s DNS name. For example, if you use DNS to look
      up the name www.ebay.com, you get the IP address of the eBay Web host:
      66.211.160.87. Thus, DNS allows you to access the eBay Web site by
      using the DNS name www.ebay.com instead of the site’s IP address.

      The following sections describe the basic concepts of DNS.
322     Understanding DNS Names


              Domains and domain names
              To provide a unique DNS name for every host computer on the Internet, DNS
              uses a time-tested technique: Divide and conquer. DNS uses a hierarchical
              naming system that’s similar to how folders are organized hierarchically on
              a Windows computer. Instead of folders, however, DNS organizes its names
              into domains. Each domain includes all the names that appear directly
              beneath it in the DNS hierarchy.

              For example, Figure 4-1 shows a small portion of the DNS domain tree. At
              the very top of the tree is the root domain, which is the anchor point for
              all domains. Directly beneath the root domain are four top-level domains,
              named edu, com, org, and gov.



                                                                    (Root)




                                       edu                 com                 org       gov




                                             LoweWriter
                                                                 LoweWriter.com domain



                         doug         debbie              server1            printer1

                                               server1.LoweWriter.com.
Figure 4-1:
DNS names.



              In reality, many more top-level domains than this exist in the Internet’s root
              domain. For more information, see the section “Top-Level Domains” later in
              this chapter.

              Beneath the com domain in Figure 4-1 is another domain called LoweWriter,
              which happens to be my own personal domain. (Pretty clever, eh?) To
              completely identify this domain, you have to combine it with the name of
              its parent domain (in this case, com) to create the complete domain name:
              LoweWriter.com. Notice that the parts of the domain name are separated
              from each other with periods, which are called dots. As a result, when you
              read this domain name, you pronounce it LoweWriter dot com.
                                    Understanding DNS Names           323

Beneath the LoweWriter node are four host nodes, named doug, debbie,
server1, and printer1. Respectively, these correspond to three computers
and a printer on my home network. You can combine the host name with
the domain name to get the complete DNS name for each of my network’s
hosts. For example, the complete DNS name for my server is server1.
LoweWriter.com. Likewise, my printer is printer1.LoweWriter.com.

Here are a few additional details that you need to remember about DNS names:

 ✦ DNS names are not case sensitive. As a result, LoweWriter and
   Lowewriter are treated as the same name, as are LOWEWRITER,
   LOWEwriter, and LoWeWrItEr. When you use a domain name, you can
   use capitalization to make the name easier to read, but DNS ignores the
   difference between capital and lowercase letters.
 ✦ The name of each DNS node can be up to 63 characters long (not
   including the dot) and can include letters, numbers, and hyphens.
    No other special characters are allowed.
 ✦ A subdomain is a domain that’s beneath an existing domain. For
   example, the com domain is actually a subdomain of the root domain.
   Likewise, LoweWriter is a subdomain of the com domain.
 ✦ DNS is a hierarchical naming system that’s similar to the hierarchical
   folder system used by Windows.
    However, one crucial difference exists between DNS and the Windows
    naming convention. When you construct a complete DNS name, you
    start at the bottom of the tree and work your way up to the root. Thus,
    doug is the lowest node in the name doug.LoweWriter.com. In
    contrast, Windows paths are the opposite: They start at the root and
    work their way down. For example, in the path \Windows\System32\
    dns, dns is the lowest node.
 ✦ The DNS tree can be up to 127 levels deep. However, in practice, the
   DNS tree is pretty shallow. Most DNS names have just three levels (not
   counting the root). And although you’ll sometimes see names with four        Book IV
   or five levels, you’ll rarely see more levels than that.                    Chapter 4

 ✦ Although the DNS tree is shallow, it’s very broad. In other words, each
   of the top-level domains has a huge number of second-level domains
                                                                                     Using DNS

   immediately beneath it. For example, at the time of this writing, the com
   domain had well over a million second-level domains beneath it.


Fully qualified domain names
If a domain name ends with a trailing dot, that trailing dot represents the
root domain, and the domain name is said to be a fully qualified domain
name (also known as an FQDN). A fully qualified domain name is also called
an absolute name. A fully qualified domain name is unambiguous because it
324   Top-Level Domains


         identifies itself all the way back to the root domain. In contrast, if a domain
         name doesn’t end with a trailing dot, the name may be interpreted in the
         context of some other domain. Thus, DNS names that don’t end with a
         trailing dot are called relative names.

         This is similar to how relative and absolute paths work in Windows. For
         example, if a path begins with a backslash, such as \Windows\System32\
         dns, the path is absolute. However, a path that doesn’t begin with a backslash,
         such as System32\dns, uses the current directory as its starting point. If
         the current directory happens to be \Windows, then \Windows\System32\
         dns and System32\dns refer to the same location.

         In many cases, relative and fully qualified domain names are interchangeable
         because the software that interprets them always interprets relative names
         in the context of the root domain. That’s why, for example, you can type
         www.wiley.com (without the trailing dot) — not www.wiley.com — to go
         to the Wiley home page in a Web browser. Some applications, such as DNS
         servers, may interpret relative names in the context of a domain other than
         the root.



Top-Level Domains
         A top-level domain appears immediately beneath the root domain. Top-level
         domains come in two categories: generic domains and geographic domains.
         These categories are described in the following sections. (Actually, a third
         type of top-level domain exists, which is used for reverse lookups. I describe
         it later in this chapter, in the section, “Reverse Lookup Zones.”)


         Generic domains
         Generic domains are the popular top-level domains that you see most often
         on the Internet. Originally, seven top-level organizational domains existed.
         In 2002, seven more were added to help ease the congestion of the original
         seven — in particular, the com domain.

         Table 4-1 summarizes the original seven generic top-level domains. Of these,
         you can see that the com domain is far and away the most populated, with
         nearly 1.9 million second-level domains beneath it.

         The Size column in this table indicates approximately how many second-level
         domains existed under each top-level domain as of January 2007, according
         to an Internet Software Consortium survey, found at www.isc.org.
                                                     Top-Level Domains   325

  Table 4-1            The Original Seven Top-Level Domains
  Domain       Description                                  Size
  com          Commercial organizations                     1,291,296
  edu          Educational institutions                     3,873
  gov          U.S. government institutions                 966
  int          International treaty organizations           119
  mil          U.S. military institutions                   110
  net          Network providers                            253,741
  org          Noncommercial organizations                  140,968


Because the com domain ballooned to an almost unmanageable size in the
late 1990s, the Internet authorities approved seven new top-level domains
in an effort to take some of the heat off of the com domain. Most of these
domains, listed in Table 4-2, became available in 2002. As you can see, they
haven’t really caught on yet even though they’ve been around for several
years.



  Table 4-2            The New Seven Top-Level Domains
  Domain                Description                         Size
  aero                  Aerospace industry                  147
  biz                   Business                            11,399
  coop                  Cooperatives                        263
  info                  Informational sites                 16,276
  museum                Museums                             11
  name                  Individual users                    710
                                                                                Book IV
  pro                   Professional organizations          30                 Chapter 4
                                                                                     Using DNS

Geographic domains
Although the top-level domains are open to anyone, U.S. companies and
organizations dominate them. An additional set of top-level domains
corresponds to international country designations. Organizations outside
the United States often use these top-level domains to avoid the congestion
of the generic domains.
326   Top-Level Domains


         Table 4-3 lists those geographic top-level domains with more than 200
         registered subdomains at the time of this writing, in alphabetical order. In
         all, about 150 geographic top-level domains exist. The exact number varies
         from time to time as political circumstances change.



           Table 4-3              Geographic Top-Level Domains with
                                     More Than 200 Subdomains
           Domain      Description              Domain      Description
           ac          Ascension Island         hu          Hungary
           ae          United Arab Emirates     ie          Ireland
           ag          Antigua and Barbuda      in          India
           am          Armenia                  is          Iceland
           an          Netherlands Antilles     it          Italy
           as          American Samoa           jp          Japan
           at          Austria                  kz          Kazakhstan
           be          Belgium                  la          Lao People’s Democratic
                                                            Republic
           bg          Bulgaria                 li          Liechtenstein
           br          Brazil                   lk          Sri Lanka
           by          Belarus                  lt          Lithuania
           bz          Belize                   lu          Luxembourg
           ca          Canada                   lv          Latvia
           cc          Cocos (Keeling)          ma          Morocco
                       Islands
           ch          Switzerland              md          Moldova
           cl          Chile                    nl          Netherlands
           cn          China                    no          Norway
           coop        Cooperatives             nu          Niue
           cx          Christmas Island         pl          Poland
           cz          Czech Republic           pt          Portugal
           de          Germany                  ro          Romania
           dk          Denmark                  ru          Russian Federation
           ee          Estonia                  se          Sweden
           es          Spain                    si          Slovenia
           eu          European Union           sk          Slovakia
                                                             The Hosts File       327

         Domain      Description                Domain      Description
         fi          Finland                    st          Sao Tome and Principe
         fm          Micronesia                 su          Soviet Union
         fo          Faroe Islands              to          Tonga
         fr          France                     tv          Tuvalu
         ge          Georgia                    tw          Taiwan
         gov         Government                 ua          Ukraine
         gr          Greece                     us          United States
         hr          Croatia                    ws          Samoa




The Hosts File
       Long ago, in a network far, far away, the entire Internet was small enough
       that network administrators could keep track of it all in a simple text file.
       This file, called the Hosts file, simply listed the name and IP address of every
       host on the network. Each computer had its own copy of the Hosts file. The
       trick was keeping all those Hosts files up to date. Whenever a new host was
       added to the Internet, each network administrator would manually update
       his copy of the Hosts file to add the new host’s name and IP address.

       As the Internet grew, so did the Hosts file. In the mid-1980s, it became obvious
       that a better solution was needed. Imagine trying to track the entire Internet
       today by using a single text file to record the name and IP address of the
       millions of hosts on the Internet! DNS was invented to solve this problem.

       Understanding the Hosts file is important for two reasons:

        ✦ The Hosts file is not dead. For small networks, a Hosts file may still be
          the easiest way to provide name resolution for the network’s computers.            Book IV
          In addition, a Hosts file can coexist with DNS. The Hosts file is always          Chapter 4
          checked before DNS is used, so you can even use a Hosts file to override
          DNS if you want.
        ✦ The Hosts file is the precursor to DNS. DNS was devised to circumvent
                                                                                                  Using DNS


          the limitations of the Hosts file. You’ll be in a better position to appreciate
          the benefits of DNS when you understand how the Hosts file works.

       The Hosts file is a simple text file that contains lines that match IP addresses
       with host names. You can edit the Hosts file with any text editor, including
       Notepad or by using the MS-DOS EDIT command. The exact location of the
       Hosts file depends on the client operating system, as listed in Table 4-4.
328   The Hosts File



             Table 4-4                    Location of the Hosts File
             Operating System           Location of Hosts File
             Windows 9x/Me              c:\windows\hosts
             Windows NT/2000            c:\winnt\system32\drivers\etc\hosts
             Windows XP and Vista       c:\windows\system32\drivers\etc\hosts
             Unix/Linux                 /etc/hosts


         All TCP/IP implementations are installed with a starter Hosts file. For example,
         Listing 4-1 shows the sample Windows 7 TCP/IP Hosts file. As you can see,
         the starter file begins with some comments that explain the purpose of the file.

         The Windows 7 Hosts file ends with comments which show the host mapping
         commands used to map for the host name localhost, mapped to the IP
         address 127.0.0.1. The IP address 127.0.0.1 is the standard loopback
         address. As a result, this entry allows a computer to refer to itself by using
         the name localhost.

         Note that after the 127.0.0.1 localhost entry, another localhost entry
         defines the standard IPv6 loopback address (::2). This is required because
         unlike previous versions of Windows, Vista provides built-in support for IPv6.

         Prior to Windows 7, these lines were not commented out in the Hosts file.
         But beginning with Windows 7, the name resolution for localhost is handled
         by DNS itself, so its definition isn’t required in the Hosts file.


         Listing 4-1: A Sample Hosts File
         #   Copyright (c) 1993-2009 Microsoft Corp.
         #
         #   This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
         #
         #   This file contains the mappings of IP addresses to host names. Each
         #   entry should be kept on an individual line. The IP address should
         #   be placed in the first column followed by the corresponding host name.
         #   The IP address and the host name should be separated by at least one
         #   space.
         #
         #   Additionally, comments (such as these) may be inserted on individual
         #   lines or following the machine name denoted by a ‘#’ symbol.
         #
         #   For example:
         #
         #        102.54.94.97      rhino.acme.com           # source server
         #         38.25.63.10      x.acme.com               # x client host

         # localhost name resolution is handled within DNS itself.
         #127.0.0.1       localhost
         #::1             localhost
                                                        The Hosts File       329

To add an entry to the Hosts file, simply edit the file in any text editor. Then,
add a line at the bottom of the file, after the localhost entry. Each line
that you add should list the IP address and the host name that you want
to use for the address. For example, to associate the host name server1.
LoweWriter.com with the IP address 192.168.168.201, you add this line
to the Hosts file:

192.168.168.201 server1.LoweWriter.com

Then, whenever an application requests the IP address of the host name
server1, the IP address 192.168.168.201 is returned.

You can also add an alias to a host mapping. This enables users to access a
host by using the alias as an alternative name. For example, consider the
following line:

192.168.168.201 server1.LoweWriter.com s1

Here, the device at address 192.168.168.201 can be accessed as
server1.LoweWriter.com or just s1.

Listing 4-2 shows a Hosts file with several hosts defined.


Listing 4-2: A Hosts File with Several Hosts Defined
#   Copyright (c) 1993-2009 Microsoft Corp.
#
#   This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
#   This file contains the mappings of IP addresses to host names. Each
#   entry should be kept on an individual line. The IP address should
#   be placed in the first column followed by the corresponding host name.
#   The IP address and the host name should be separated by at least one
#   space.
#
#   Additionally, comments (such as these) may be inserted on individual
#   lines or following the machine name denoted by a ‘#’ symbol.                     Book IV
#                                                                                   Chapter 4
#   For example:
#
#        102.54.94.97     rhino.acme.com         # source server
#         38.25.63.10     x.acme.com             # x client host
                                                                                          Using DNS


# localhost name resolution is handled within DNS itself.
# 127.0.0.1       localhost
# ::1             localhost

192.168.168.200    doug.LoweWriter.com           #Doug’s computer
192.168.168.201    server1.LoweWriter.com s1     #Main server
192.168.168.202    debbie.LoweWriter.com         #Debbie’s computer
192.168.168.203    printer1.LoweWriter.com p1    #HP Laser Printer

Even if your network uses DNS, every client still has a Hosts file that defines
at least localhost.
330   Understanding DNS Servers and Zones


Understanding DNS Servers and Zones
         A DNS server is a computer that runs DNS server software, helps to maintain
         the DNS database, and responds to DNS name resolution requests from
         other computers. Although many DNS server implementations are available,
         the two most popular are Bind and the Windows DNS service. Bind runs
         on Unix-based computers (including Linux computers), and Windows DNS
         (naturally) runs on Windows computers. Both provide essentially the same
         services and can interoperate.

         The key to understanding how DNS servers work is to realize that the DNS
         database — that is, the list of all the domains, subdomains, and host
         mappings — is a massively distributed database. No single DNS server
         contains the entire DNS database. Instead, authority over different parts of
         the database is delegated to different servers throughout the Internet.

         For example, suppose that I set up a DNS server to handle name resolutions
         for my LoweWriter.com domain. Then, when someone requests the IP
         address of doug.LoweWriter.com, my DNS server can provide the answer.
         However, my DNS server wouldn’t be responsible for the rest of the Internet.
         Instead, if someone asks my DNS server for the IP address of some other
         computer, such as coyote.acme.com, my DNS server will have to pass the
         request on to another DNS server that knows the answer.


         Zones
         To simplify the management of the DNS database, the entire DNS namespace
         is divided into zones, and the responsibility for each zone is delegated to a
         particular DNS server. In many cases, zones correspond directly to domains.
         For example, if I set up a domain named LoweWriter.com, I can also set
         up a DNS zone called LoweWriter.com that’s responsible for the entire
         LoweWriter.com domain.

         However, the subdomains that make up a domain can be parceled out to
         separate zones, as shown in Figure 4-2. Here, a domain named LoweWriter.
         com has been divided into two zones. One zone, us.LoweWriter.com, is
         responsible for the entire us.LoweWriter.com subdomain. The other zone,
         LoweWriter.com, is responsible for the entire LoweWriter.com domain
         except for the us.LoweWriter.com subdomain.

         Why would you do that? The main reason is to delegate authority for the
         zone to separate servers. For example, Figure 4-2 suggests that part of the
         LoweWriter.com domain is administered in the United States and that part
         of it is administered in France. The two zones in the figure allow one server
         to be completely responsible for the U.S. portion of the domain, and the
         other server handles the rest of the domain.
                                            Understanding DNS Servers and Zones                       331

                                                                      (Root)




                                                               com




                                                  LoweWriter



                                                   LoweWriter.com zone
                                                                               france
                            us




                                     us.LoweWriter.com
Figure 4-2:                                zone
DNS zones.




                        The old phony Hosts file trick
   The Hosts file can be the basis of a fun, prac-        151.124.250.181 www.espn.com
   tical joke. Of course, neither I nor my editors       Now, whenever your husband tries to call up
   or publishers recommend that you actually do          the ESPN Web site, he’ll get the Carnival Cruise
   this. If it gets you into trouble, don’t send your    Lines home page instead.                               Book IV
   lawyers to me. This sidebar is here only to let
                                                                                                               Chapter 4
   you know what to do if it happens to you.             Of course, to actually pull a stunt like this would
                                                         be completely irresponsible. Especially if you
   The idea is to edit your poor victim’s Hosts          didn’t first make a backup copy of the Hosts
   file so that whenever the user tries to access
                                                                                                                     Using DNS

                                                         file, just in case it somehow gets messed up.
   his favorite Web site, a site of your choosing
   comes up instead. For example, if you’re trying       Be warned: If the wrong Web sites suddenly
   to get your husband to take you on a cruise,          start coming up, check your Hosts file to see
   add a line to his Hosts file that replaces his        whether it’s been tampered with.
   favorite Web site with the Web site for a cruise
   line. For example, this line should do the trick:
332   Understanding DNS Servers and Zones


         The following are the two basic types of zones:

          ✦ A primary zone is the master copy of a zone. The data for a primary
            zone is stored in the local database of the DNS server that hosts the
            primary zone. Only one DNS server can host a particular primary zone.
            Any updates to the zone must be made to the primary zone.
          ✦ A secondary zone is a read-only copy of a zone. When a server hosts a
            secondary zone, the server doesn’t store a local copy of the zone data.
            Instead, it obtains its copy of the zone from the zone’s primary server by
            using a process called zone transfer. Secondary servers must periodically
            check primary servers to see whether their secondary zone data is still
            current. If not, a zone transfer is initiated to update the secondary zone.


         Primary and secondary servers
         Each DNS server is responsible for one or more zones. The following are the
         two different roles that a DNS server can take:

          ✦ Primary server for a zone, which means that the DNS server hosts a
            primary zone. The data for the zone is stored in files on the DNS server.
            Every zone must have one primary server.
          ✦ Secondary server for a zone, which means that the DNS server obtains
            the data for a secondary zone from a primary server. Every zone should
            have at least one secondary server. That way, if the primary server goes
            down, the domain defined by the zone can be accessed via the secondary
            server or servers.

         A secondary server should be on a different subnet than the zone’s primary
         server. If the primary and secondary servers are on the same subnet, both
         servers will be unavailable if the router that controls the subnet goes down.

         Note that a single DNS server can be the primary server for some zones and
         a secondary server for other zones. A server is said to be authoritative for
         the primary and secondary zones that it hosts because it can provide
         definitive answers for queries against those zones.


         Root servers
         The core of DNS comprises the root servers, which are authoritative for
         the entire Internet. The main function of the root servers is to provide the
         address of the DNS servers that are responsible for each of the top-level
         domains. These servers, in turn, can provide the DNS server address for
         subdomains beneath the top-level domains.

         The root servers are a major part of the glue that holds the Internet
         together. As you can imagine, they’re swamped with requests day and night.
         A total of 13 root servers are located throughout the world. Table 4-5 lists
         the IP address and location of each of the 13 root servers.
                         Understanding DNS Servers and Zones              333

  Table 4-5                      The 13 Root Servers
  Server    IP Address              Operator               Location
  A         198.41.0.4              VeriSign Global        Dulles, VA
                                    Registry Services
  B         192.228.79.201          Information            Marina Del Rey, CA
                                    Sciences Institute
  C         192.33.4.12             Cogent                 Herndon, VA and
                                    Communications         Los Angeles, CA
  D         128.8.10.90             University of          College Park, MD
                                    Maryland
  E         192.203.230.10          NASA Ames              Mountain View, CA
                                    Research Center
  F         192.5.5.241             Internet Systems       Palo Alto, CA; San
                                    Consortium             Jose, CA; New York
                                                           City; San Francisco;
                                                           Madrid; Hong Kong;
                                                           Los Angeles
  G         192.112.36.4            U.S. DOD Network       Vienna, VA Center
                                    Information
  H         128.63.2.53             U.S. Army              Aberdeen, MD
                                    Research Lab
  I         192.36.148.17           Autonomica             Stockholm
  J         192.58.128.30           VeriSign Global        Dulles, VA;
                                    Registry Services      Mountain View CA;
                                                           Sterling, VA (two
                                                           locations); Seattle,
                                                           WA; Amsterdam,
                                                           NL; Atlanta, GA; Los
                                                           Angeles
  K         193.0.14.129            Reseaux IP             London                  Book IV
                                    Europeens              Coordination Centre    Chapter 4
                                    Network
  L         199.7.83.42             IANA                   Los Angeles
                                                                                        Using DNS

  M         202.12.27.33            WIDE Project           Tokyo


DNS servers learn how to reach the root servers by consulting a root hints
file that’s located on the server. In the Unix/Linux world, this file is known
as named.root and can be found at /etc/named.root. For Windows
DNS servers, the file is called cache.dns and can be found in \windows\
system32\dns\ or \winnt\system32\dns\, depending on the Windows
version. Listing 4-3 shows the file itself.
334   Understanding DNS Servers and Zones


         Listing 4-3: The Named.Root File
         ;       This file holds the information on root name servers needed to
         ;       initialize cache of Internet domain name servers
         ;       (e.g. reference this file in the “cache . <file>”
         ;       configuration file of BIND domain name servers).
         ;
         ;       This file is made available by InterNIC
         ;       under anonymous FTP as
         ;            file                 /domain/named.root
         ;            on server            FTP.INTERNIC.NET
         ;       -OR-                      RS.INTERNIC.NET
         ;
         ;       last update:     Dec 12, 2008
         ;       related version of root zone:      2008121200
         ;
         ; formerly NS.INTERNIC.NET
         ;
         .                         3600000 IN NS        A.ROOT-SERVERS.NET.
         A.ROOT-SERVERS.NET.       3600000       A      198.41.0.4
         A.ROOT-SERVERS.NET.       3600000       AAAA 2001:503:BA3E::2:30
         ;
         ; FORMERLY NS1.ISI.EDU
         ;
         .                         3600000       NS     B.ROOT-SERVERS.NET.
         B.ROOT-SERVERS.NET.       3600000       A      192.228.79.201
         ;
         ; FORMERLY C.PSI.NET
         ;
         .                         3600000       NS     C.ROOT-SERVERS.NET.
         C.ROOT-SERVERS.NET.       3600000       A      192.33.4.12
         ;
         ; FORMERLY TERP.UMD.EDU
         ;
         .                         3600000       NS     D.ROOT-SERVERS.NET.
         D.ROOT-SERVERS.NET.       3600000       A      128.8.10.90
         ;
         ; FORMERLY NS.NASA.GOV
         ;
         .                         3600000       NS     E.ROOT-SERVERS.NET.
         E.ROOT-SERVERS.NET.       3600000       A      192.203.230.10
         ;
         ; FORMERLY NS.ISC.ORG
         ;
         .                         3600000       NS     F.ROOT-SERVERS.NET.
         F.ROOT-SERVERS.NET.       3600000       A      192.5.5.241
         F.ROOT-SERVERS.NET.       3600000       AAAA 2001:500:2F::F
         ;
         ; FORMERLY NS.NIC.DDN.MIL
         ;
         .                         3600000       NS     G.ROOT-SERVERS.NET.
         G.ROOT-SERVERS.NET.       3600000       A      192.112.36.4
         ;
         ; FORMERLY AOS.ARL.ARMY.MIL
         ;
         .                         3600000       NS     H.ROOT-SERVERS.NET.
         H.ROOT-SERVERS.NET.       3600000       A      128.63.2.53
         H.ROOT-SERVERS.NET.       3600000       AAAA 2001:500:1::803F:235
         ;
         ; FORMERLY NIC.NORDU.NET
         ;
         .                         3600000       NS     I.ROOT-SERVERS.NET.
                                           Understanding DNS Queries           335

      I.ROOT-SERVERS.NET.      3600000     A      192.36.148.17
      ;
      ; OPERATED BY VERISIGN, INC.
      ;
      .                        3600000     NS     J.ROOT-SERVERS.NET.
      J.ROOT-SERVERS.NET.      3600000     A      192.58.128.30
      J.ROOT-SERVERS.NET.      3600000     AAAA   2001:503:C27::2:30
      ;
      ; OPERATED BY RIPE NCC
      ;
      .                        3600000     NS     K.ROOT-SERVERS.NET.
      K.ROOT-SERVERS.NET.      3600000     A      193.0.14.129
      K.ROOT-SERVERS.NET.      3600000     AAAA   2001:7FD::1
      ;
      ; OPERATED BY ICANN
      ;
      .                        3600000     NS     L.ROOT-SERVERS.NET.
      L.ROOT-SERVERS.NET.      3600000     A      199.7.83.42
      L.ROOT-SERVERS.NET.      3600000     AAAA   2001:500:3::42
      ;
      ; OPERATED BY WIDE
      ;
      .                        3600000     NS     M.ROOT-SERVERS.NET.
      M.ROOT-SERVERS.NET.      3600000     A      202.12.27.33
      M.ROOT-SERVERS.NET.      3600000     AAAA   2001:DC3::35
      ; End of File



      Caching
      DNS servers don’t really like doing all that work to resolve DNS names, but
      they’re not stupid. They know that if a user visits www.wiley.com today,
      he’ll probably do it again tomorrow. As a result, name servers keep a cache
      of query results. The next time the user visits www.wiley.com, the name
      server is able to resolve this name without having to query all those other
      name servers.

      The Internet is constantly changing, however, so cached data can quickly
      become obsolete. For example, suppose that Wiley Publishing, Inc., switches
      its Web site to a different server? It can update its name servers to reflect
      the new IP address, but any name servers that have a cached copy of the
      query will be out of date.                                                          Book IV
                                                                                         Chapter 4
      To prevent this from being a major problem, DNS data is given a relatively
      short expiration time. The expiration value for DNS data is called the TTL
      (Time to Live). TTL is specified in seconds. Thus, a TTL of 60 means the data
                                                                                               Using DNS


      is kept for one minute.



Understanding DNS Queries
      When a DNS client needs to resolve a DNS name to an IP address, it uses a
      library routine — a resolver — to handle the query. The resolver takes care of
      sending the query message over the network to the DNS server, receiving and
      interpreting the response, and informing the client of the results of the query.
336   Understanding DNS Queries


         A DNS client can make two basic types of queries: recursive and iterative.
         The following list describes the difference between these two query types.
         (The following discussion assumes that the client is asking the server for the
         IP address of a host name, which is the most common type of DNS query.
         You find out about other types of queries later; they, too, can be either
         recursive or iterative.)

          ✦ Recursive queries: When a client issues a recursive DNS query, the
            server must reply with either the IP address of the requested host name
            or an error message indicating that the host name doesn’t exist. If the
            server doesn’t have the information, it asks another DNS server for the
            IP address. When the first server finally gets the IP address, it sends it
            back to the client. If the server determines that the information doesn’t
            exist, it returns an error message.
          ✦ Iterative queries: When a server receives an iterative query, it returns
            the IP address of the requested host name if it knows the address. If the
            server doesn’t know the address, it returns a referral, which is simply
            the address of a DNS server that should know. The client can then issue
            an iterative query to the server to which it was referred.

         Normally, DNS clients issue recursive queries to DNS servers. If the server
         knows the answer to the query, it replies directly to the client. If not, the
         server issues an iterative query to a DNS server that it thinks should know
         the answer. If the original server gets an answer from the second server,
         it returns the answer to the client. If the original server gets a referral to a
         third server, the original server issues an iterative query to the third server.
         The original server keeps issuing iterative queries until it either gets the
         answer or an error occurs. It then returns the answer or the error to the
         client.


         A real-life DNS example
         Confused? I can understand why. An example may help to clear things up.
         Suppose that a user wants to view the Web page www.wiley.com. The
         following sequence of steps occurs to resolve this address:

         1. The browser asks the client computer’s resolver to find the IP address
             of www.wiley.com.
         2. The resolver issues a recursive DNS query to its name server.
             In this case, I’ll call the name server ns1.LoweWriter.com.
         3. The name server ns1LoweWriter.com checks whether it knows the IP
             address of www.wiley.com.
             It doesn’t, so the name server issues an iterative query to one of the root
             name servers to see whether it knows the IP address of www.wiley.com.
                                       Zone Files and Resource Records          337

       4. The root name server doesn’t know the IP address of www.wiley.com,
           so it returns a list of the name servers that are authoritative for the com
           domain.
       5. The ns1.LoweWriter.com name server picks one of the com domain
           name servers and sends it an iterative query for www.wiley.com.
       6. The com name server doesn’t know the IP address of www.wiley.com,
           so it returns a list of the name servers that are authoritative for the
           wiley.com domain.
       7. The ns1.LoweWriter.com name server picks one of the name
           servers for the wiley.com domain and sends it an iterative query for
           www.wiley.com.
       8. The wiley.com name server knows the IP address for www.wiley.com,
           so the name server returns it.
       9. The ns1.LoweWriter.com name server shouts with joy for having
           finally found the IP address for www.wiley.com. It gleefully returns this
           address to the client. It also caches the answer so that the next time the
           user looks for www.wiley.com, the name server won’t have to contact
           other name servers to resolve the name.
      10. The client also caches the results of the query.
           The next time the client needs to look for www.wiley.com, the client
           can resolve the name without troubling the name server.



Zone Files and Resource Records
       Each DNS zone is defined by a zone file (also known as a DNS database or a
       master file). For Windows DNS servers, the name of the zone file is domain.
       zone. For example, the zone file for the LoweWriter.com zone is named
       LoweWriter.com.zone. For BIND DNS servers, the zone files are named
       db.domain. Thus, the zone file for the LoweWriter.com domain would be
       db.LoweWriter.com. The format of the zone file contents is the same for            Book IV
       both systems, however.                                                            Chapter 4

       A zone file consists of one or more resource records. Creating and updating
       the resource records that comprise the zone files is one of the primary tasks
                                                                                               Using DNS

       of a DNS administrator. The Windows DNS server provides a friendly graphical
       interface to the resource records. However, you should still be familiar with
       how to construct resource records.

       Resource records are written as simple text lines, with the following fields:

       Owner     TTL     Class     Type     RDATA
338   Zone Files and Resource Records


         These fields must be separated from each other by one or more spaces. The
         following list describes the five resource record fields:

          ✦ Owner: The name of the DNS domain or the host that the record applies
            to. This is usually specified as a fully qualified domain name (with a
            trailing dot) or as a simple host name (without a trailing dot), which is
            then interpreted in the context of the current domain.
               You can also specify a single @ symbol as the owner name. In that case,
               the current domain is used.
          ✦ TTL: Also known as Time to Live; the number of seconds that the record
            should be retained in a server’s cache before it’s invalidated. If you omit
            the TTL value for a resource record, a default TTL is obtained from the
            Start of Authority (SOA) record.
          ✦ Class: Defines the protocol to which the record applies. You should
            always specify IN, for the Internet protocol. If you omit the class field,
            the last class field that you specified explicitly is used. As a result, you’ll
            sometimes see zone files that specify IN only on the first resource
            record (which must be an SOA record) and then allow it to default to IN
            on all subsequent records.
          ✦ Type: The resource record type. The most commonly used resource
            types are summarized in Table 4-6 and are described separately later
            in this section. Like the Class field, you can also omit the Type field and
            allow it to default to the last specified value.
          ✦ RDATA: Resource record data that is specific to each record type.



           Table 4-6                  Common Resource Record Types
           Type             Name                   Description
           SOA              Start of Authority     Identifies a zone
           NS               Name Server            Identifies a name server that is authori-
                                                   tative for the zone
           A                Address                Maps a fully qualified domain name to
                                                   an IP address
           CNAME            Canonical Name         Creates an alias for a fully qualified
                                                   domain name
           MX               Mail Exchange          Identifies the mail server for a domain
           PTR              Pointer                Maps an IP address to a fully qualified
                                                   domain name for reverse lookups


         Most resource records fit on one line. If a record requires more than one
         line, you must enclose the data that spans multiple lines in parentheses.
                                  Zone Files and Resource Records                339

You can include comments to clarify the details of a zone file. A comment
begins with a semicolon and continues to the end of the line. If a line begins
with a semicolon, the entire line is a comment. You can also add a comment
to the end of a resource record. You see examples of both types of comments
later in this chapter.


SOA records
Every zone must begin with an SOA record, which names the zone and
provides default information for the zone. Table 4-7 lists the fields that
appear in the RDATA section of an SOA record. Note that these fields are
positional, so you should include a value for all of them and list them in the
order specified. Because the SOA record has so many RDATA fields, you’ll
probably need to use parentheses to continue the SOA record onto multiple
lines.



  Table 4-7                RDATA Fields for an SOA Record
  Name          Description
  MNAME         The domain name of the name server that is authoritative for the zone.
  RNAME         An e-mail address (specified in domain name format; not regular
                e-mail format) of the person responsible for this zone.
  SERIAL        The serial number of the zone. Secondary zones use this value to
                determine whether they need to initiate a zone transfer to update
                their copy of the zone.
  REFRESH       A time interval that specifies how often a secondary server should
                check whether the zone needs to be refreshed. A typical value is
                3600 (one hour).
  RETRY         A time interval that specifies how long a secondary server should
                wait after requesting a zone transfer before trying again. A typical
                value is 600 (ten minutes).
  EXPIRE        A time interval that specifies how long a secondary server should keep     Book IV
                the zone data before discarding it. A typical value is 86400 (one day).   Chapter 4

  MINIMUM       A time interval that specifies the TTL value to use for zone resource
                records that omit the TTL field. A typical value is 3600 (one hour).
                                                                                                Using DNS




Note two things about the SOA fields:

 ✦ The e-mail address of the person responsible for the zone is given in
   DNS format, not in normal e-mail format. Thus, you separate the user
   from the mail domain with a dot rather than an @ symbol. For example,
   doug@LoweWriter.com would be listed as doug.lowewriter.com.
340   Zone Files and Resource Records


          ✦ The serial number should be incremented every time you change
            the zone file. If you edit the file via the graphic interface provided
            by Windows DNS, the serial number is incremented automatically.
            However, if you edit the zone file via a simple text editor, you have to
            manually increment the serial number.

         Here’s a typical example of an SOA record, with judicious comments to
         identify each field:

         lowewriter.com. IN SOA (
             ns1.lowewriter.com               ;   authoritative name server
             doug.lowewriter.com              ;   responsible person
             148                              ;   version number
             3600                             ;   refresh (1 hour)
             600                              ;   retry (10 minutes)
             86400                            ;   expire (1 day)
             3600 )                           ;   minimum TTL (1 hour)



         NS records
         Name Server (NS) records identify the name servers that are authoritative
         for the zone. Every zone must have at least one NS record. Using two or
         more NS records is better so that if the first name server is unavailable, the
         zone will still be accessible.

         The owner field should either be the fully qualified domain name for the
         zone, with a trailing dot, or an @ symbol. The RDATA consists of just one
         field: the fully qualified domain name of the name server.

         The following examples show two NS records that serve the lowewriter.
         com domain:

         lowewriter.com.       IN     NS   ns1.lowewriter.com.
         lowewriter.com.       IN     NS   ns2.lowewriter.com.


         A records
         Address (A) records are the meat of the zone file: They provide the IP
         addresses for each of the hosts that you want to make accessible via DNS.
         In an A record, you usually list just the host name in the owner field, thus
         allowing DNS to add the domain name to derive the fully qualified domain
         name for the host. The RDATA field for the A record is the IP address of the
         host.

         The following lines define various hosts for the LoweWriter.com domain:

         doug           IN   A      192.168.168.200
         server1        IN   A      192.168.168.201
         debbie         IN   A      192.168.168.202
         printer1       IN   A      192.168.168.203
         router1        IN   A      207.126.127.129
         www            IN   A      64.71.129.102
                                 Zone Files and Resource Records           341

Notice that for these lines, I don’t specify the fully qualified domain names
for each host. Instead, I just provide the host name. DNS will add the name of
the zone’s domain to these host names in order to create the fully qualified
domain names.

If I wanted to be more explicit, I could list these A records like this:

doug.lowewriter.com.             IN    A   192.168.168.200
server1.lowewriter.com.          IN    A   192.168.168.201
debbie.lowewriter.com.           IN    A   192.168.168.202
printer1.lowewriter.com.         IN    A   192.168.168.203
router1.lowewriter.com           IN    A   207.126.127.129
www.lowewriter.com.              IN    A   64.71.129.102

However, all this does is increase the chance for error. Plus, it creates more
work for yourself later if you decide to change your network’s domain.


CNAME records
A Canonical Name (CNAME) record creates an alias for a fully qualified
domain name. When a user attempts to access a domain name that is actually
an alias, the DNS system substitutes the real domain name — known as the
Canonical Name — for the alias. The owner field in the CNAME record provides
the name of the alias that you want to create. Then, the RDATA field provides
the Canonical Name — that is, the real name of the host.

For example, consider these resource records:

ftp.lowewriter.com.           IN    A        207.126.127.132
files.lowewriter.com.         IN    CNAME    www1.lowewriter.com.

Here, the host name of an FTP server at 207.126.127.132 is ftp.lowe
writer.com. The CNAME record allows users to access this host as files.
lowewriter.com if they prefer.

                                                                                  Book IV
PTR records                                                                      Chapter 4
A Pointer (PTR) record is the opposite of an address record: It provides the
fully qualified domain name for a given address. The owner field should
specify the reverse lookup domain name, and the RDATA field specifies the
                                                                                       Using DNS


fully qualified domain name. For example, the following record maps the
address 64.71.129.102 to www.lowewriter.com:

102.129.71.64.in-addr.arpa. IN             PTR   www.lowewriter.com.

PTR records don’t usually appear in normal domain zones. Instead, they
appear in special reverse lookup zones. For more information, see the section,
“Reverse Lookup Zones,” later in this chapter.
342   Reverse Lookup Zones


         MX records
         Mail Exchange (MX) records identify the mail server for a domain. The
         owner field provides the domain name that users address mail to. The
         RDATA section of the record has two fields. The first is a priority number
         used to determine which mail servers to use when several are available.
         The second is the fully qualified domain name of the mail server itself.

         For example, consider the following MX records:

         lowewriter.com.         IN   MX   0    mail1.lowewriter.com.
         lowewriter.com.         IN   MX   10   mail2.lowewriter.com.

         In this example, the lowewriter.com domain has two mail servers, named
         mail1.lowewriter.com and mail2.lowewriter.com. The priority
         numbers for these servers are 0 and 10. Because it has a lower priority
         number, mail will be delivered to mail1.lowewriter.com first. The
         mail2.lowewriter.com server will be used only if mail1.lowewriter.
         com isn’t available.

         The server name specified in the RDATA section should be an actual host
         name, not an alias created by a CNAME record. Although some mail servers
         can handle MX records that point to CNAMEs, not all can. As a result, you
         shouldn’t specify an alias in an MX record.

         Be sure to create a reverse lookup record (PTR, described in the next
         section) for your mail servers. Some mail servers won’t accept mail from a
         server that doesn’t have valid reverse lookup entries.



Reverse Lookup Zones
         Normal DNS queries ask a name server to provide the IP address that
         corresponds to a fully qualified domain name. This kind of query is a forward
         lookup. A reverse lookup is the opposite of a forward lookup: It returns the
         fully qualified domain name of a host based on its IP address.

         Reverse lookups are possible because of a special domain called the in-
         addr.arpa domain, which provides a separate fully qualified domain name
         for every possible IP address on the Internet. To enable a reverse lookup for
         a particular IP address, all you have to do is create a PTR record in a reverse
         lookup zone (a zone that is authoritative for a portion of the in-addr.arpa
         domain). The PTR record maps the in-addr.arpa domain name for the
         address to the host’s actual domain name.

         The technique used to create the reverse domain name for a given IP
         address is pretty clever. It creates subdomains beneath the in-addr.arpa
         domain by using the octets of the IP address, listing them in reverse order.
         For example, the reverse domain name for the IP address 207.126.67.129
         is 129.67.126.207.in-addr.arpa.
                              Working with the Windows DNS Server             343

      Why list the octets in reverse order? Because that correlates the network
      portions of the IP address (which work from left to right) with the subdomain
      structure of DNS names (which works from right to left). The following
      description should clear this up:

       ✦ The 255 possible values for the first octet of an IP address each have a
         subdomain beneath the in-addr.arpa domain. For example, any IP
         address that begins with 207 can be found in the 207.in-addr.arpa
         domain.
       ✦ Within this domain, each of the possible values for the second octet can
         be found as a subdomain of the first octet’s domain. Thus, any address
         that begins with 207.126 can be found in the 126.207.in-addr.arpa
         domain.
       ✦ The same holds true for the third octet, so any address that begins with
         207.126.67 can be found in the 67.126.207.in-addr.arpa domain.
       ✦ By the time you get to the fourth octet, you’ve pinpointed a specific host.
         The fourth octet completes the fully qualified reverse domain name. Thus,
         207.126.67.129 is mapped to 129.67.126.207.in-addr.arpa.

      As a result, to determine the fully qualified domain name for the computer
      at 207.126.67.129, the client queries its DNS server for the FQDN that
      corresponds to 129.67.126.207.in-addr.arpa.



Working with the Windows DNS Server
      Installing and managing a DNS server depends on the network operating
      system that you’re using. The following sections are specific to working with
      a DNS server in Windows 2003. Working with BIND in a Unix/Linux environment
      is similar but without the help of a graphical user interface (GUI).

      You can install the DNS server on Windows Server 2008 from the Server
      Manager application. Choose Start➪Administrative Tools➪Server Manager.             Book IV
      Click the Server Roles, click the Add Roles link, and then follow the wizard      Chapter 4
      instructions to add the DNS role.

      After you set up a DNS server, you can manage the DNS server from the
                                                                                              Using DNS

      DNS management console, as shown in Figure 4-3. From this management
      console, you can perform common administrative tasks, such as adding
      additional zones, changing zone settings, adding A or MX records to an
      existing zone, and so on. The DNS management console hides the details
      of the actual resource records from you, thus allowing you to work with a
      friendly GUI instead.

      To add a new host (that is, an A record) to a zone, right-click the zone in the
      DNS management console and choose the Add New Host command. This
      brings up the New Host dialog box, as shown in Figure 4-4. From this dialog
      box, specify the following information:
344      Working with the Windows DNS Server




Figure 4-3:
The DNS
management
console.




Figure 4-4:
The New
Host
dialog box.



              ✦ Name: The host name for the new host.
              ✦ IP Address: The host’s IP address.
              ✦ Create Associated Pointer (PTR) Record: Automatically creates a PTR
                record in the reverse lookup zone file. Select this option if you want to
                allow reverse lookups for the host.
              ✦ Allow Any Authenticated User to Update: Select this option if you want
                to allow other users to update this record or other records with the
                same host name. You should usually leave this option deselected.

              You can add other records, such as MX or CNAME records, in the same way.
                                    How to Configure a Windows DNS Client            345

How to Configure a Windows DNS Client
              Client computers don’t need much configuration in order to work properly
              with DNS. The client must have the address of at least one DNS server.
              Usually, this address is supplied by DHCP, so if the client is configured to
              obtain its IP address from a DHCP server, it will also obtain the DNS server
              address from DHCP.

              To configure a client computer to obtain the DNS server location from
              DHCP, bring up the Network Properties dialog box by choosing Network
              or Network Connections in Control Panel (depending on which version of
              Windows the client is running). Then, select the Internet Protocol Version
              4 (TCP/IPv4) protocol and click the Properties button. This summons the
              dialog box shown in Figure 4-5. To configure the computer to use Dynamic
              Host Configuration Protocol (DHCP), select the Obtain an IP Address
              Automatically and the Obtain DNS Server Address Automatically options.




Figure 4-5:
Configuring
a Windows
client to
obtain
its DNS
address
from DHCP.
                                                                                              Book IV
                                                                                             Chapter 4


              If the computer doesn’t use DHCP, you can use this same dialog box to
              manually enter the IP address of your DNS server.
                                                                                                   Using DNS
346   Book IV: TCP/IP and the Internet
       Chapter 5: Using FTP
       In This Chapter
       ✓ Figuring out the basics of FTP
       ✓ Setting up an FTP server
       ✓ Retrieving files from an FTP server
       ✓ Using FTP commands




       F    ile Transfer Protocol (FTP) is the basic method for exchanging files over
            the Internet. If you need to access files from someone’s FTP site, this
       chapter shows you how to do so by using a Web browser or a command
       line FTP client. If you need to set up your own FTP server to share files with
       other users, this chapter shows you how to do that, too.



Discovering FTP
       FTP is as old as the Internet. The first versions of FTP date to the early
       1970s, and even the current FTP standard (RFC 959) dates to 1985. You can
       use FTP with the command line FTP client (which has a decidedly 1980s feel
       to it), or you can access FTP sites with most modern Web browsers if you
       prefer a graphic interface. Old computer hounds prefer the FTP command
       line client, probably for nostalgic reasons.

       In spite of its age, FTP is still commonly used on the Internet. For example,
       InterNIC (the organization that manages Internet names) maintains an FTP
       site at ftp.rs.internic.net. There, you can download important files,
       such as named.root, which provides the current location of the Internet’s
       root name servers. Many other companies maintain FTP sites from which
       you can download software, device drivers, documentation, reports, and
       so on. FTP is also one of the most common ways to publish HTML files to a
       Web server. Because FTP is still so widely used, it pays to know how to use
       it from both the command line and from a browser.

       In the Windows world, an FTP server is integrated with the Microsoft Web
       server, Internet Information Services (IIS). As a result, you can manage FTP
       from the IIS management console along with other IIS features. Note that
       the FTP component is an optional part of IIS, so you may need to install it
       separately if you opted to not include it when you first installed IIS.
348   Configuring an FTP Server


         On Unix and Linux systems, FTP isn’t usually integrated with a Web server.
         Instead, the FTP server is installed as a separate program. You’re usually
         given the option to install FTP when you install the operating system. If you
         choose not to, you can always install it later.

         When you run an FTP server, you expose a portion of your file system to the
         outside world. As a result, you need to be careful about how you set up your
         FTP server so that you don’t accidentally allow hackers access to the bowels
         of your file server. Fortunately, the default configuration of FTP is pretty
         secure. You shouldn’t tinker much with the default configuration unless you
         know what you’re doing.



Configuring an FTP Server
         In the following sections, I show you how to configure FTP services in
         Microsoft IIS. The examples show IIS version 6 running on Windows Server
         2008, but the procedures are essentially the same for other IIS versions.


         Installing FTP
         Although FTP is integrated with IIS, FTP is not installed by default when you
         install IIS. As a result, if you didn’t specifically select FTP when you installed
         IIS, you need to install FTP before you can set up an FTP site. Here are the
         procedures for Windows Server 2003 and 2008:

          ✦ For Windows Server 2003, you install the FTP protocol by choosing
            Control Panel➪Add or Remove Programs➪Add/Remove Windows
            Components. Then, select Application Server from the list of components,
            click Details, and choose Internet Information Services (IIS). Click Details
            again and then select File Transfer Protocol (FTP) from the list of IIS
            subcomponents. Finally, click OK to install FTP. If asked, you’ll need to
            insert the Windows Server 2003 setup disc.
          ✦ For Windows Server 2008, choose Start➪Server Manager and select the
            Web Server (IIS) role. Scroll down to the Role Services section and
            then click Add Role Services. Select the FTP Server role, click Next,
            and then click Install.


         Creating an FTP site
         After you install FTP, you must create at least one FTP site. To do that,
         follow these steps:

          1. Choose Start➪Administrative Programs➪Internet Information Services
             (IIS) Manager.
             This launches the IIS Manager console, as shown in Figure 5-1.
                                                    Configuring an FTP Server        349




Figure 5-1:
The IIS
management
console.



               2. Right-click the Sites node and choose Add FTP Site.
                  The first page of the Add FTP Site Wizard appears, as shown in Figure 5-2.




Figure 5-2:
The Add FTP
                                                                                                Book IV
Site Wizard
                                                                                               Chapter 5
asks for the
name and
data folder
                                                                                                     Using FTP

for the FTP
site.



               3. Enter a name for your ftp site.
                  In Figure 5-2, I entered the name ftp.
350      Configuring an FTP Server


               4. Enter the path to the folder that will hold the FTP site’s data.
                  This field determines the location on the server where the data stored
                  on the FTP site will be located. If you don’t know the exact path, click
                  the Browse button and browse to the folder location.
               5. Click Next.
                  The second page of the Add FTP Site Wizard appears, as shown in
                  Figure 5-3. This page lets you set the port number that the FTP site will
                  use, and lets you indicate whether you will use SSL security.




Figure 5-3:
The second
page of the
Add FTP
Site Wizard.



               6. Leave the IP Address and Port fields unchanged unless you want to
                  use a nonstandard port.
                  By default, the FTP site will use port 21, which is the standard port for
                  the FTP protocol.
               7. Select the SSL security option you want to use.
                  If you have an SSL certificate and want to use SSL security, select either
                  Allow SSL or Require SSL. If you select Allow SSL, users can access your
                  site with or without SSL security. If you select Require SSL, users must
                  always use SSL security to access the FTP site.
                  If you don’t have a certificate available or if the site will contain data
                  that doesn’t require tight security, select No SSL.
               8. Click Next.
                  The third page of the Add FTP Site Wizard appears, as shown in Figure
                  5-4. This page lets you set the basic login security to be used for the site.
                                                      Configuring an FTP Server        351




Figure 5-4:
The third
page of the
Add FTP
Site Wizard.



                9. Select the Anonymous option if you want to allow anonymous users to
                   access your FTP site.
                   If you check this option, users can access your FTP site without providing
                   any login information. You should specify this option only for sites that
                   have no security requirements.
               10. Select the Basic option if you want to allow Basic authentication.
                   This option allows users to log in using a Windows username and
                   password. Note that because this option transmits the password in
                   unencrypted form, you should use it only when you know that the
                   connection between the user and the FTP server is secure.
               11. Select the user access permissions you want to grant.
                   You can grant Read and Write permissions to All Users (as shown in the
                   figure), to anonymous users, and to individual users or groups.
                   Do not grant Write permissions to anonymous users. If you do, your FTP        Book IV
                                                                                                Chapter 5
                   site will quickly become a dumping ground for all kinds of trash as word
                   gets out about your totally unsecured FTP site.
               12. Click Finish.
                                                                                                      Using FTP


                   Your FTP site is created!


               Changing the FTP site properties
               You can change the properties for an FTP site by selecting the site in IIS
               Manager. This brings up a page with several icons that let you change
               various settings for the site, as shown in Figure 5-5.
352      Configuring an FTP Server




Figure 5-5:
The FTP Site
page.



               The FTP Site Properties dialog box contains the following tabs that let you
               configure the properties of your FTP site:

                ✦ FTP Authentication: Lets you enable or disable Anonymous and Basic
                  authentication for the FTP site.
                ✦ FTP Authorization: Lets you grant access rights to individual users,
                  groups of users, anonymous users, or all users.
                ✦ Current Sessions: Displays a list of users who are currently accessing
                  the FTP site.
                ✦ FTP Directory Browsing: Sets several options that determine how users
                  can browse the data directories in the FTP site.
                ✦ FTP Firewall Support: Sets several advanced options for working with
                  firewalls. Best leave these settings alone unless you’re a firewall guru.
                ✦ FTP IPv4 Address and Domain Restrictions: You can use this page to
                  grant or deny access to users based on their IP addresses or domain
                  names. This page is useful if you want to restrict access to a specific set
                  of users.
                ✦ FTP Logging: Lets you control logging for the site.
                ✦ FTP Messages: Lets you create four customized messages that appear
                  when users access the site, as shown in Figure 5-6.
                                                     Configuring an FTP Server        353




Figure 5-6:
Customizing
the site’s
messages.



                  The four messages you can configure are:
                   • The Banner message appears when a user first accesses the site,
                     before he or she has logged on. If the site allows anonymous logons,
                     you may mention that in the Banner message.
                   • The Welcome message appears after the user has successfully logged
                     on to your site.
                   • The Exit message appears when the user leaves the site.
                   • The Maximum Connections message appears when the connection
                     limit has been exceeded.


              Adding content to your FTP site
              When you set up an FTP site, the data for the site is stored in a folder on one
              of the server’s disks. To make your FTP site useful, you’ll need to add files      Book IV
              to this folder. Those files will then be available for download on the site.      Chapter 5
              The easiest way to do that is to simply open Windows Explorer, browse to
              the folder, and copy the files you want to include. If you’re not sure where
              the site’s home folder is located, you can find it by opening the site in IIS
                                                                                                      Using FTP


              Manager and choosing the site in the IIS Manager and clicking Basic Settings
              in the task pane on the right side of the screen.
354   Accessing an FTP Site with a Browser


         The following list offers some useful tips for setting up FTP site content:

          ✦ Create a readme.txt file in the FTP site’s home directory that
            describes the content and rules for your site. Hopefully, users will view
            this file when they visit your site. There’s no guarantee that they will,
            but you can always hope.
          ✦ If your site has a lot of files, organize them into subdirectories
            beneath the home directory.
          ✦ Stick to short filenames. Users working with command line clients
            appreciate brevity because they’ll have to type the filenames accurately
            to retrieve your files.
          ✦ Don’t use spaces in filenames. Some clients balk at names that include
            spaces.



Accessing an FTP Site with a Browser
         Modern Web browsers include built-in support for FTP. Internet Explorer
         lets you access an FTP site almost as if it were a local disk. You can even
         drag and drop files to and from an FTP site.

         To access an FTP site in a Web browser, just type the name of the site in
         the address bar. If you want, you can explicitly specify the FTP protocol by
         typing ftp:// before the FTP site name, but that’s usually not necessary. The
         browser determines that the name you type is an FTP site and invokes the
         FTP protocol automatically.

         Figure 5-7 shows you how a typical FTP site appears when accessed with
         Windows Explorer on a Windows 7 system. As you can see, the files and
         folders appear as if they were on a local disk. Double-click a folder to display
         the files contained in that folder; download files by dragging them from the
         browser window to the desktop or to another window. You can also upload
         files by dragging them from the desktop or another window into the FTP
         browser window.

         If the contents of an FTP site don’t appear in the browser window, you
         may need to log on to the site. Choose File➪Login As to display the Log
         On As dialog box. If the site administrator has given you a name and
         password, you can enter it here to access the site. Otherwise, select the
         Log On Anonymously check box and then click the Log On button.
                                          Using an FTP Command Line Client          355




Figure 5-7:
Browsing an
FTP site.




Using an FTP Command Line Client
              If you’re a command line junkie, you’ll appreciate the FTP command that
              comes with Windows. It isn’t pretty, but it gets the job done. At the end
              of this chapter, you can find a command reference that details all the
              subcommands you can use with the FTP command. In this section, I just
              show you a typical session in which I sign on to an FTP server named ftp.
              lowewriter.com, switch to a directory named pics, download a file, and
              then log off.

              First, open a command window: Choose Start➪Run, type Command in the
              text box, and then click OK. Navigate to the directory to where you want to
              download files. This step is important because, although you can change the
              local working directory from within the FTP command, it’s much easier to         Book IV
              just start FTP from the right directory.                                        Chapter 5

              To start FTP, type ftp with the name of the FTP server as the parameter, like
              this:
                                                                                                    Using FTP



              C:\>ftp ftp.lowewriter.com
356   Using an FTP Command Line Client


         Assuming that you typed the site name correctly, the FTP command connects
         to the site, displays the banner message, and prompts you to log on:

         Connected to ftp.lowewriter.com.
         220-Microsoft FTP Service
         220 We have 999 spooks here, but there’s always room for one
            more! To volunteer, log in as Anonymous.
         User (ftp.lowewriter.com:(none)):

         To log on anonymously, type Anonymous and then press Enter. The server
         responds by telling you that Anonymous access is allowed and asks for your
         e-mail address as a password:

         331 Anonymous access allowed, send identity (e-mail name) as
            password.
         Password:

         Type your e-mail address as the password and then press Enter. The
         Welcome message appears, followed by the ftp> prompt:

         230-Welcome to my FTP site! For spooky Halloween pictures,
            check out the Pics folder.
         230 Anonymous user logged in.
         ftp>

         Whenever you see the ftp> prompt, the FTP command is waiting for you to
         enter a subcommand. Start by entering dir to see a directory listing:

         200 PORT command successful.
         150 Opening ASCII mode data connection   for /bin/ls.
         06-30-07 08:05PM        <DIR>            pics
         06-30-07 07:55PM                  2365   readme.txt
         06-30-07 07:55PM        <DIR>            sounds
         06-30-07 07:56PM        <DIR>            videos
         226 Transfer complete.
         ftp: 190 bytes received in 0.00Seconds   190000.00Kbytes/sec.
         ftp>

         As you can see, the response from the dir command isn’t quite as clean as
         the display from an MS-DOS command. Still, you can pick out that the directory
         includes three subdirectories, named pics, sounds, and videos, and a
         single file, named readme.txt. The size of the file is 2,365 bytes.

         Here’s a good question: If you enter a dir command, why does the response
         read 200 PORT command successful? The answer has to do with how
         the FTP protocol works. When you enter a dir command, the FTP client
         forwards a PORT command to the server that opens a data transfer port that
         is then used to return the resulting directory listing. The server replies that
         the PORT command has successfully opened a data transfer port. Then, it
         sends back the directory listing. Finally, it sends two more lines: one to
         indicate that the transfer is complete (that is, that the dir output has been
         successfully sent), and the other to summarize the number of bytes of data
         that were sent and the data transfer rate.
                             Using an FTP Command Line Client           357

The files that I want to download are located in the pics subdirectory, so
the next command to issue is cd pics. This results in the following output:

250 CWD command successful.
ftp>

Once again, the command’s output isn’t exactly what you’d expect. The FTP
protocol doesn’t actually have a CD command. Instead, it uses a command
named CWD, which stands for change working directory, to change the directory.
The Windows FTP client uses command CD instead of CWD to be more
consistent with the Windows/MS-DOS user interface, which uses the command
CD to change directories. When you type a CD command at the ftp> prompt,
the FTP client sends a CWD command to the FTP server. The server then
replies with the message CWD command successful to indicate that the
directory has been changed.

Next, type dir again. The FTP server displays the directory listing for the
pics directory:

200 PORT command successful.
150 Opening ASCII mode data connection   for /bin/ls.
06-27-07 10:04PM                123126   door.jpg
06-27-07 10:06PM                112457   echair.jpg
06-27-07 10:06PM                 81610   fence.jpg
06-27-07 10:09PM                138102   fog.jpg
06-27-07 10:09PM                 83712   gallows.jpg
06-27-07 10:10PM                166741   ghost.jpg
06-27-07 09:58PM                119859   skel01.jpg
06-27-07 10:05PM                 87720   wall.jpg
226 Transfer complete.
ftp: 400 bytes received in 0.00Seconds   400000.00Kbytes/sec.
ftp>

Here, you can see that the pics directory contains eight files. To download
a file, you use the GET command, specifying the name of the file that you
want to download. For example, to download the door.jpg file, type get
door.jpg. The FTP server transfers the file to your computer and displays
the following response:                                                           Book IV
                                                                                 Chapter 5
200 PORT command successful.
150 Opening ASCII mode data connection for door.jpg(123126 bytes).
226 Transfer complete.
ftp: 123126 bytes received in 0.13Seconds 985.01Kbytes/sec.
                                                                                       Using FTP

ftp>

Notice again that the response indicates that the command actually processed
by the server is a PORT command. The file is transferred in ASCII mode.
The entire transfer takes 0.13 seconds, which works out to a transfer rate of
about 985K per second.

After you download the file, you can end the session by typing bye. FTP
responds by displaying the site’s goodbye message; then it returns you to
the MS-DOS command prompt:
358   FTP Command and Subcommand Reference


         221 Hurry back...
         C:\>

         Of course, FTP is a lot more involved than this simple session suggests. Still,
         the most common use of FTP is to download files, and most downloads are
         no more complicated than this example.



FTP Command and Subcommand Reference
         The rest of this chapter is an FTP command reference. In the following
         sections, you can find complete reference information for the FTP
         command and all its subcommands. The first command described is the
         FTP command itself. After that, all the FTP command subcommands are listed
         in alphabetical order.


         The FTP command
         What it does:         Starts the FTP client so that you can transfer files to
                               and from an FTP server

         Syntax:               ftp [-v] [-d] [-i] [-n] [-g] [-s:filename] [-a]
                               [-w:windowsize] [-A] [host]

         Parameters:           -v     Turns off Verbose mode.

                               -d     Turns on Debug mode.

                               -i     Turns off Prompt mode.

                               -n     Forces manual logon.

                               -g     Turns off Glob mode.

                               -s     Specifies a script file that contains FTP commands.

                               -a     Specifies that any network interface can be
                                      used to bind the data connection.

                               -w     Specifies the size of the transmission buffer.
                                      The default is 4K.

                               -A     Automatically logs on as Anonymous.

         Host:                 The FTP server to which you want to connect.
                               This can be the server’s DNS name or an IP address.

         Examples:             ftp ftp.lowewriter.com
                               ftp ftp.lowewriter.com -A
                FTP Command and Subcommand Reference              359

More info:       Unlike most Windows commands, the switches for this
                 command begin with a hyphen, not a slash.

                 If you want to script subcommands, use the -s switch.
                 Input redirection doesn’t work with FTP.

                 When FTP is running, the prompt ftp> appears.
                 When this prompt is displayed, you can enter any of
                 the FTP subcommands described in the rest of this
                 chapter.


! (Escape)
What it does:    Escape to a command shell

Syntax:          !

More info:       This command brings up a temporary command prompt
                 so that you can enter commands. To return to the ftp>
                 prompt, type exit.


? (Help)
What it does:    Displays Help information

Syntax:          ? [command]

                 help [command]

Example:         help mput

More info:       ? and help are interchangeable. If you enter ? or help
                 by itself, a list of FTP commands appears. If you enter
                 ? or help followed by a command name, a summary of
                 that command’s function appears.                           Book IV
                                                                           Chapter 5

append
What it does:    Uploads a file and appends it to the end of an existing
                                                                                 Using FTP


                 file on the remote system

Syntax:          append localfile [remotefile]

Example:         append extra.txt start.txt

More info:       If you omit the remotefile parameter, the remote file
                 is assumed to have the same name as the local file.
360   FTP Command and Subcommand Reference


         ascii
         What it does:   Sets the ASCII transfer mode

         Syntax:         ascii

         More info:      This command sets the transfer type of ASCII, which is
                         best suited for text files. ASCII is the default transfer
                         type.


         bell
         What it does:   Causes the FTP client to beep when each transfer is
                         complete

         Syntax:         bell

         More info:      This command is useful when you’re downloading long
                         files and want to take a nap during the download.
                         Unfortunately, it doesn’t beep when it sees your boss
                         approaching your office, so you’ll need some other
                         alarm system to cover that contingency.


         binary
         What it does:   Sets the binary transfer type

         Syntax:         binary

         More info:      The binary file type is best for executable files and
                         other nontext files.


         bye
         What it does:   Ends the FTP session and exits the FTP client

         Syntax:         bye

         More info:      This is the command to use when you’re done. It’s the
                         same as the quit command.


         cd
         What it does:   Changes the working directory on the remote computer

         Syntax:         cd remotedirectory

         Example:        cd pics
                FTP Command and Subcommand Reference               361

More info:       Use this to change to the directory that contains the
                 files you want to download or the directory to which
                 you want to upload files.

                 Type cd \ to go to the root directory.


close
What it does:    Closes the session with the remote computer but
                 doesn’t leave the FTP program

Syntax:          close

More info:       You can use this command if you want to switch to
                 another FTP server without leaving and restarting the
                 FTP program. This command is the same as the
                 disconnect command.


debug
What it does:    Toggles Debug mode

Syntax:          debug

More info:       When Debug mode is on, the FTP client displays the
                 actual FTP commands that are sent to the FTP server.
                 This can be useful if you’re an FTP guru trying to
                 diagnose a problem with a server or a client, but it can
                 also be fun if you just want to see how FTP client
                 commands (like CD) get translated into FTP server
                 commands (like CWD).


delete
What it does:    Deletes the specified file on the remote computer            Book IV
                                                                             Chapter 5
Syntax:          delete remotefile

Example:         delete fright.txt
                                                                                   Using FTP



More info:       You can delete only one file at a time with this command.
                 To delete more than one file in a single command, use
                 the mdelete command.


dir
What it does:    Lists contents of remote directory

Syntax:          dir [remotedirectory] [localfile]
362   FTP Command and Subcommand Reference


         Examples:       dir
                         dir \pics
                         dir \pics picdir.txt

         More info:      The first parameter lets you list a directory other than
                         the current working directory. The second parameter lets
                         you capture the output to a file on the local computer.


         disconnect
         What it does:   Disconnects from the remote computer but doesn’t
                         leave the FTP program

         Syntax:         disconnect

         More info:      You can use this command if you want to switch to
                         another FTP server without leaving and restarting the
                         FTP program. This command is the same as the close
                         command.


         get
         What it does:   Downloads a file from the remote computer

         Syntax:         get remotefile [localfile]

         Examples:       get boo.exe
                         get boo.exe bar.exe

         More info:      This command downloads the specified file from the
                         current working directory on the remote system to the
                         current directory on the local system. The second
                         parameter lets you save the file using a different name
                         than the name used on the remote system.

                         You can use this command to download only one file
                         at a time. To download multiple files, use the mget
                         command.

                         This command is the same as the recv command.


         glob
         What it does:   Toggles the use of wildcards for local filenames

         Syntax:         glob

         More info:      If globbing is on, you can use * and ? characters in
                         local filenames. Globbing is on by default.
                FTP Command and Subcommand Reference                363

hash
What it does:    Toggles the display of hash marks (#) to indicate
                 transfer progress

Syntax:          hash

More info:       Hash is off by default. If you turn it on by issuing the
                 hash command, a hash mark (#) appears each time a
                 2K data block is transferred. This helps you track the
                 progress of transfers.


help
What it does:    Displays Help information

Syntax:          ? [command]

                 help [command]

Example:         help mput

More info:       ? and help are interchangeable. If you enter ? or help
                 by itself, a list of FTP commands appears. If you enter
                 ? or help followed by a command name, a summary of
                 that command’s function appears.


lcd
What it does:    Changes the working directory on the local computer

Syntax:          lcd localdirectory

Example:         lcd \docs
                                                                             Book IV
More info:       Use this to change to the directory you want to            Chapter 5
                 download files to or that contains files you want to
                 upload.                                                          Using FTP


literal
What it does:    Sends a native FTP command directly to the server

Syntax:          literal arguments . . .

Example:         literal cwd pics

More info:       Use this command if you’re an FTP guru and you want
                 to send a native FTP command to the server. It’s the
                 same as the quote command.
364   FTP Command and Subcommand Reference


         ls
         What it does:   List contents of remote directory

         Syntax:         ls [remotedirectory] [localfile]

         Examples:       ls
                         ls \pics
                         ls \pics picdir.txt

         More info:      The first parameter lets you list a directory other than
                         the current working directory. The second parameter
                         lets you capture the output to a file on the local computer.


         mdelete
         What it does:   Delete multiple files

         Syntax:         mdelete remotefile . . .

         Examples:       mdelete file1.txt
                         mdelete file1.txt file2.txt file3.txt

         More info:      This command deletes one or more files from the
                         current working directory on the remote system.


         mdir
         What it does:   Lists the contents of multiple remote directories

         Syntax:         mdir remotedirectory . . . [localfile]

         Example:        mdir pics videos

         More info:      Specify a hyphen as the last parameter to display the
                         output on the screen. Otherwise, the last parameter
                         will be interpreted as the name of the local file you
                         want the directory listing captured to.


         mget
         What it does:   Downloads multiple files

         Syntax:         mget remotefile . . .

         Examples:       mget file1.txt
                         mget file1.txt file2.txt file3.txt
                FTP Command and Subcommand Reference                 365

More info:       This command downloads one or more files from the
                 current working directory on the remote system to the
                 current directory on the local computer.


mkdir
What it does:    Creates a directory on the remote system

Syntax:          mkdir remotedirectory

Example:         mdir plans

More info:       The new subdirectory is created in the current working
                 directory on the remote system.


mls
What it does:    Lists the contents of multiple remote directories

Syntax:          mls remotedirectory . . . [localfile]

Example:         mls pics videos

More info:       Specify a hyphen as the last parameter to display the
                 output on the screen. Otherwise, the last parameter
                 will be interpreted as the name of the local file you
                 want the directory listing captured to.


mput
What it does:    Uploads multiple files

Syntax:          mput localfile . . .

Examples:        mput file1.txt                                             Book IV
                 mput file1.txt file2.txt file3.txt                        Chapter 5

More info:       This command uploads one or more files from the
                 current directory on the local system to the current
                                                                                 Using FTP


                 working directory on the remote system.


open
What it does:    Connects to an FTP server

Syntax:          open remotesystem [port]
366   FTP Command and Subcommand Reference


         Examples:       open ftp.microsoft.com
                         open ftp.weirdport.com 1499

         More info:      Specify the port number only if the remote system
                         does not use the standard FTP ports (20 and 21).


         prompt
         What it does:   Toggles prompting for multiple transfers

         Syntax:         prompt

         More info:      When Prompt mode is on, you’re prompted for each
                         file before the file is transferred. Prompt mode is on by
                         default.


         put
         What it does:   Uploads a file to the remote computer

         Syntax:         put localfile [remotefile]

         Examples:       put boo.exe
                         put boo.exe bar.exe

         More info:      This command uploads the specified file from the
                         current directory on the local system to the current
                         working directory on the remote system. The second
                         parameter lets you save the file with a different name
                         than the name used on the local system.

                         You can use this command to upload only one file at a
                         time. To upload multiple files, use the mput command.

                         This command is the same as the send command.


         pwd
         What it does:   Displays the current working directory on the remote
                         computer

         Syntax:         pwd

         More info:      If you aren’t sure what the current directory is on the
                         remote system, use this command to find out.
                FTP Command and Subcommand Reference              367

quit
What it does:    Ends the FTP session and quits the FTP program

Syntax:          quit

More info:       This is the command to use when you’re done. It’s the
                 same as the bye command.


quote
What it does:    Sends a native FTP command directly to the server

Syntax:          quote arguments . . .

Example:         quote cwd pics

More info:       Use this command if you’re an FTP guru and you want
                 to send a native FTP command to the server. It’s the
                 same as the literal command.


recv
What it does:    Downloads a file from the remote computer

Syntax:          recv remotefile [localfile]

Examples:        recv boo.exe
                 recv boo.exe bar.exe

More info:       This command downloads the specified file from the
                 current working directory on the remote system to the
                 current directory on the local system. The second
                 parameter lets you save the file with a different name
                 than the name used on the remote system.
                                                                           Book IV
                                                                          Chapter 5
                 You can use this command to download only one file at
                 a time. To download multiple files, use the mget
                 command.
                                                                                Using FTP


                 This command is the same as the get command.
368   FTP Command and Subcommand Reference


         remotehelp
         What it does:   Displays help for remote commands

         Syntax:         remotehelp [command]

         Example:        remotehelp cwd

         More info:      If you enter remotehelp by itself, a list of FTP
                         commands is displayed. If you enter remotehelp
                         followed by a command name, a summary of that
                         command’s function appears.


         rename
         What it does:   Renames a file on the remote system

         Syntax:         rename filename newfilename

         Example:        rename door.jpg doorway.jpg

         More info:      Use this command to change the name of a file on the
                         remote system.


         rmdir
         What it does:   Removes a directory on the remote system

         Syntax:         rmdir directoryname

         Example:        rmdir oldpics

         More info:      This command removes a directory and all the files in
                         it, so use it with caution!


         send
         What it does:   Uploads a file to the remote computer

         Syntax:         send localfile [remotefile]

         Examples:       send boo.exe
                         send boo.exe bar.exe
                FTP Command and Subcommand Reference               369

More info:       This command uploads the specified file from the
                 current directory on the local system to the current
                 working directory on the remote system. The second
                 parameter lets you save the file with a different name
                 than the name used on the local system.

                 You can use this command to upload only one file at a
                 time. To upload multiple files, use the mput command.

                 This command is the same as the put command.


status
What it does:    Displays the current status of the FTP client

Syntax:          status

More info:       Use this command to display the current settings of
                 options, such as bell, prompt, and verbose, as well
                 as the current connection status.


trace
What it does:    Activates Trace mode

Syntax:          trace

More info:       When Trace mode is on, detailed information about
                 each packet transmission is displayed. trace is off by
                 default and should be left off unless you’re digging
                 deep into the bowels of FTP or just want to show off.


type
What it does:    Sets the transfer type to ASCII or binary or displays the    Book IV
                 current mode                                                Chapter 5

Syntax:          type [ascii or binary]
                                                                                   Using FTP


Examples:        type ascii
                 type binary
                 type
370   FTP Command and Subcommand Reference


         More info:      Use ASCII transfers for text files, and use binary
                         transfers for nontext files.

                         If you don’t specify a type, the current transfer type
                         appears.

                         You can also use the ascii or binary command to
                         switch the transfer type.


         user
         What it does:   Logs you on to a remote system

         Syntax:         user username [password]

         Examples:       user doug
                         user doug notmypw

         More info:      This command logs you on to the remote system by
                         using the username and password you provide. If you
                         omit the password, you’re prompted to enter it.


         verbose
         What it does:   Toggles Verbose mode

         Syntax:         verbose

         More info:      When Verbose mode is on, FTP responses appear.
                         Verbose mode is on by default.
      Chapter 6: TCP/IP Tools
      and Commands
      In This Chapter
      ✓ Recognizing tools and commands
      ✓ Making all your hosts sing with IPConfig and Ping




      M      ost client and server operating systems that support Transmission
             Control Protocol/Internet Protocol (TCP/IP) come with a suite of
      commands and tools that are designed to let you examine TCP/IP configuration
      information and diagnose and correct problems. Although the exact form of
      these commands varies between Windows and Unix/Linux, most are
      surprisingly similar. This chapter is a reference to the most commonly used
      TCP/IP commands.



Using the arp Command
      Using the arp command allows you to display and modify the Address
      Resolution Protocol (ARP) cache. An ARP cache is a simple mapping of IP
      addresses to MAC addresses. Each time a computer’s TCP/IP stack uses ARP
      to determine the Media Access Control (MAC) address for an IP address, it
      records the mapping in the ARP cache so that future ARP lookups go faster.

      If you use the arp command without any parameters, you get a list of the
      command’s parameters. To display the ARP cache entry for a specific IP
      address, use an -a switch followed by the IP address. For example:

      C:\>arp -a 192.168.168.22
      Interface: 192.168.168.21 --- 0x10004
        Internet Address      Physical Address                 Type
        192.168.168.22        00-60-08-39-e5-a1                dynamic
      C:\>
372   Using the hostname Command


         You can display the complete ARP cache by using -a without specifying an
         IP address, like this:

         C:\>arp -a
         Interface: 192.168.168.21 --- 0x10004
           Internet Address      Physical Address                Type
           192.168.168.9         00-02-e3-16-e4-5d               dynamic
           192.168.168.10        00-50-04-17-66-90               dynamic
           192.168.168.22        00-60-08-39-e5-a1               dynamic
           192.168.168.254       00-40-10-18-42-49               dynamic
         C:\>

         ARP is sometimes useful when diagnosing duplicate IP assignment problems.
         For example, suppose you can’t access a computer that has an IP address
         of 192.168.168.100. You try to ping the computer, expecting the ping to
         fail; but lo and behold, the ping succeeds. One possible cause for this may
         be that two computers on the network have been assigned the address
         192.168.168.100, and your ARP cache is pointing to the wrong one.
         The way to find out is to go to the 192.168.168.100 computer that you
         want to access, run ipconfig /all, and make a note of the physical
         address. Then return to the computer that’s having trouble reaching the
         192.168.168.100 computer, run arp -a, and compare the physical
         address with the one you noted. If they’re different, that two computers
         are assigned the same IP address. You can then check the Dynamic Host
         Configuration Protocol (DHCP) or static TCP/IP configuration of the
         computers involved to find out why.



Using the hostname Command
         The hostname command is the simplest of all the TCP/IP commands presented
         in this chapter. It simply displays the computer’s host name. For example:

         C:\>hostname
         doug
         C:\>

         Here, the host name for the computer is doug. The Windows version of the
         hostname command has no parameters. However, the Unix/Linux versions
         of hostname let you set the computer’s host name as well as display it. You
         do that by specifying the new host name as an argument.
                                                 Using the ipconfig Command              373

Using the ipconfig Command
      Using the ipconfig command displays information about a computer’s
      TCP/IP configuration. It can also be used to update DHCP and Domain Name
      Server (DNS) settings.


      Displaying basic IP configuration
      To display the basic IP configuration for a computer, use the ipconfig
      command without any parameters, like this:

      C:\>ipconfig

      Windows IP Configuration


      Ethernet adapter Local Area Connection:

         Connection-specific DNS   Suffix    .   :
         Link-local IPv6 Address   . . . .   .   :   fe80::cca:9067:9427:a911%8
         IPv4 Address. . . . . .   . . . .   .   :   192.168.1.110
         Subnet Mask . . . . . .   . . . .   .   :   255.255.255.0
         Default Gateway . . . .   . . . .   .   :   192.168.1.1

      Tunnel adapter Local Area Connection* 6:

         Connection-specific DNS   Suffix    .   :
         IPv6 Address. . . . . .   . . . .   .   : 2001:0:4136:e38c:2c6c:670:3f57:fe91
         Link-local IPv6 Address   . . . .   .   : fe80::2c6c:670:3f57:fe91%9
         Default Gateway . . . .   . . . .   .   : ::

      Tunnel adapter Local Area Connection* 7:

         Connection-specific DNS Suffix . :
         Link-local IPv6 Address . . . . . : fe80::5efe:192.168.1.110%10
         Default Gateway . . . . . . . . . :
      C:\>

      When you use ipconfig without parameters, the command displays the
      name of the adapter, the domain name used for the adapter, the IP address,
      the subnet mask, and the default gateway configuration for the adapter. This              Book IV
                                                                                               Chapter 6
      is the easiest way to determine a computer’s IP address.
                                                                                                  TCP/IP Tools and
      If your computer indicates an IP address in the 169.254.x.x block, odds
                                                                                                    Commands


      are good that the DHCP server isn’t working. 169.254.x.x is the Class B
      address block that Windows uses when it resorts to IP Autoconfiguration.
      This usually happens only when the DHCP server can’t be reached or isn’t
      working.
374   Using the ipconfig Command


         Displaying detailed configuration information
         You can display detailed IP configuration information by using an /all
         switch with the ipconfig command, like this:

         C:\>ipconfig /all

         Windows IP Configuration

            Host Name . . . . .   .   .   .    .   .   .   .   :   WK07-001
            Primary Dns Suffix    .   .   .    .   .   .   .   :
            Node Type . . . . .   .   .   .    .   .   .   .   :   Hybrid
            IP Routing Enabled.   .   .   .    .   .   .   .   :   No
            WINS Proxy Enabled.   .   .   .    .   .   .   .   :   No

         Ethernet adapter Local Area Connection:

            Connection-specific DNS Suffix                 .   :
            Description . . . . . . . . . .     Intel(R) PRO/100 VE Network Connection
                                                           .   :
            Physical Address. . . . . . . .     00-12-3F-A7-17-BA
                                                           .   :
            DHCP Enabled. . . . . . . . . .     No         .   :
            Autoconfiguration Enabled . . .     Yes        .   :
            Link-local IPv6 Address . . . .     fe80::cca:9067:9427:a911%8(Preferred)
                                                           .   :
            IPv4 Address. . . . . . . . . .     192.168.1.110(Preferred)
                                                           .   :
            Subnet Mask . . . . . . . . . .     255.255.255.0
                                                           .   :
            Default Gateway . . . . . . . .     192.168.1.1.   :
            DNS Servers . . . . . . . . . .     192.168.1.10
                                                           .   :
                                                68.87.76.178
            NetBIOS over Tcpip. . . . . . . . : Enabled

         C:\>

         You can determine a lot of information about the computer from the
         ipconfig /all command. For example:

          ✦ The computer’s host name is WK07-001.
          ✦ The computer’s IPv4 address is 192.168.1.110, and the subnet mask
            is 255.255.255.0.
          ✦ The default gateway is a router located at 192.168.1.1.
          ✦ This router is also the network’s DHCP server.
          ✦ The DNS servers are at 192.168.1.10 and 68.87.76.178.


         Renewing an IP lease
         If you’re having an IP configuration problem, you can often solve it by
         renewing the computer’s IP lease. To do that, use a /renew switch, like this:

         C:\>ipconfig /renew
         Windows IP Configuration
         Ethernet adapter Local Area          Connection:
                 Connection-specific          DNS Suffix            .   :
                 IP Address. . . . .          . . . . . .           .   : 192.168.1.110
                 Subnet Mask . . . .          . . . . . .           .   : 255.255.255.0
                 Default Gateway . .          . . . . . .           .   : 192.168.1.1
         C:\>
                                          Using the nbtstat Command          375

      When you renew an IP lease, the ipconfig command displays the new lease
      information.

      This command won’t work if you configured the computer to use a static IP
      address.


      Releasing an IP lease
      You can release an IP lease by using an ipconfig command with the /
      release parameter, like this:

      C:\>ipconfig /release
      Windows IP Configuration
      Ethernet adapter Local Area        Connection:
              Connection-specific        DNS Suffix     .   :
              IP Address. . . . .        . . . . . .    .   : 0.0.0.0
              Subnet Mask . . . .        . . . . . .    .   : 0.0.0.0
              Default Gateway . .        . . . . . .    .   :
      C:\>

      As you can see, the DNS suffix and default gateway for the computer are
      blank, and the IP address and subnet mask are set to 0.0.0.0.

      After you release the DHCP lease, you can use an ipconfig /renew
      command to obtain a new DHCP lease for the computer.


      Flushing the local DNS cache
      You probably won’t need to do this unless you’re having DNS troubles. If
      you’ve been tinkering with your network’s DNS configuration, you may need
      to flush the cache on your DNS clients so that they’ll be forced to reacquire
      information from the DNS server. You can do that by using a /flushdns
      switch:

      C:\>ipconfig /flushdns
      Windows IP Configuration                                                         Book IV
      Successfully flushed the DNS Resolver Cache.                                    Chapter 6
      C:\>
                                                                                         TCP/IP Tools and
      Even if you don’t need to do this, it’s fun just to see the computer read
                                                                                           Commands


      flushed. If I worked at Microsoft, you’d be able to revert Windows Vista
      computers back to XP by using a /flushVista switch.



Using the nbtstat Command
      nbtstat is a Windows-only command that can help solve problems with
      NetBIOS name resolution. (nbt stands for NetBIOS over TCP/IP.) You can
      use any of the switches listed in Table 6-1 to specify what nbtstat output
376   Using the nbtstat Command


         you want to display. For example, you can use an -a switch to display the
         cached name table for a specified computer, like this:

         C:\>nbtstat -a WK07-001

         Local Area Connection:
         Node IpAddress: [192.168.1.110] Scope Id: []

                       NetBIOS Remote Machine Name Table

                   Name               Type         Status
                ---------------------------------------------
                WK07-001       <00> UNIQUE       Registered
                WORKGROUP      <00> GROUP        Registered
                WK07-001       <20> UNIQUE       Registered
                WORKGROUP      <1E> GROUP        Registered
                WORKGROUP      <1D> UNIQUE       Registered
                ..__MSBROWSE__.<01> GROUP        Registered

                MAC Address = 00-12-3F-A7-17-BAC:\>
         C:\>

         Table 6-1 lists the switches that you can use with nbtstat and explains the
         function of each switch.



           Table 6-1                   nbtstat Command Switches
           Switch                What It Does
           -a name               Lists the specified computer’s name table given the
                                 computer’s name
           -A IP-address         Lists the specified computer’s name table given the
                                 computer’s IP address
           -c                    Lists the contents of the NetBIOS cache
           -n                    Lists locally registered NetBIOS names
           -r                    Displays a count of the names resolved by broadcast and
                                 via WINS
           -R                    Purges and reloads the cached name table from the
                                 LMHOSTS file
           -RR                   Releases and then reregisters all names
           -S                    Displays the sessions table using IP addresses
           -s                    Displays the sessions table and converts destination IP
                                 addresses to computer NetBIOS names
                                                 Using the netdiag Utility      377

Using the netdiag Utility
       netdiag is a powerful, network-testing utility that performs a variety of
       network diagnostic tests that can help you to pinpoint a networking problem.
       Listing 6-1 shows the output from a typical execution of the Netdiag
       command. (I took the liberty of editing it somewhat to make it more compact.)
       You can scan this listing to see the types of tests that the netdiag command
       performs.

       Unfortunately, the netdiag command is not available for Windows 9x
       computers (including Windows Me), and it isn’t installed by default in
       Windows XP or Vista. However, you can install it in Windows XP or Vista by
       inserting your Windows installation disc in your computer’s optical drive.
       If you’re asked to reinstall Windows, say no. Instead, choose to browse the
       install CD. Navigate your way down to the \Support\Tools folder on the
       install CD and then double-click the Setup.exe icon in the \Support\Tools
       folder.

       The netdiag command has several switches that let you control the output
       generated by the command:

        ✦ /q: Lists only those tests that fail
        ✦ /v: Generates verbose output (even more verbose than usual)
        ✦ /debug: Generates extremely verbose output — way more than when
          you use /v
        ✦ /l: Stores the output from the command in a file named NetDiag.log
        ✦ /fix: Attempts to fix DNS problems that are discovered


       Listing 6-1: Output from the netdiag Command
       ...............................
           Computer Name: DOUG                                                              Book IV
           DNS Host Name: Doug
           System info : Windows 2000 Professional (Build 2600)                            Chapter 6
           Processor : x86 Family 15 Model 2 Stepping 4, GenuineIntel
           List of installed hotfixes :
                                                                                              TCP/IP Tools and
               Q147222
                                                                                                Commands


               Q308677
               Q308678
               Q310601
               Q311889
               Q315000
       Netcard queries test . . . . . . . : Passed
       Per interface results:
           Adapter : Local Area Connection
               Netcard queries test . . . : Passed
               Host Name. . . . . . . . . : Doug
               IP Address . . . . . . . . : 192.168.168.21
               Subnet Mask. . . . . . . . : 255.255.255.0
                                                                             (continued)
378   Using the netstat Command


         Listing 6-1 (continued)
                 Default Gateway. . . . . . : 192.168.168.254
                 Dns Servers. . . . . . . . : 192.168.168.10
                                               168.215.210.50
                                               192.9.9.3
                 AutoConfiguration results. . . . . . : Passed
                 Default gateway test . . . : Passed
                 NetBT name test. . . . . . : Passed
                 WINS service test. . . . . : Skipped
                     There are no WINS servers configured for this interface.
         Global results:
         Domain membership test . . . . . . : Passed
             Dns domain name is not specified.
             Dns forest name is not specified.
         NetBT transports test. . . . . . . : Passed
             List of NetBt transports currently configured:
                 NetBT_Tcpip_{4A526104-BAEB-44F0-A2F6-A804FE31BBAA}
             1 NetBt transport currently configured.
         Autonet address test . . . . . . . : Passed
         IP loopback ping test. . . . . . . : Passed
         Default gateway test . . . . . . . : Passed
         NetBT name test. . . . . . . . . . : Passed
         Winsock test . . . . . . . . . . . : Passed
         DNS test . . . . . . . . . . . . . : Passed
         Redir and Browser test . . . . . . : Passed
             List of NetBt transports currently bound to the Redir
                 NetBT_Tcpip_{4A526104-BAEB-44F0-A2F6-A804FE31BBAA}
             The redir is bound to 1 NetBt transport.
             List of NetBt transports currently bound to the browser
                 NetBT_Tcpip_{4A526104-BAEB-44F0-A2F6-A804FE31BBAA}
             The browser is bound to 1 NetBt transport.
         DC discovery test. . . . . . . . . : Skipped
         DC list test . . . . . . . . . . . : Skipped
         Trust relationship test. . . . . . : Skipped
         Kerberos test. . . . . . . . . . . : Skipped
         LDAP test. . . . . . . . . . . . . : Skipped
         Bindings test. . . . . . . . . . . : Passed
         WAN configuration test . . . . . . : Skipped
             No active remote access connections.
         Modem diagnostics test . . . . . . : Passed
         IP Security test . . . . . . . . . : Passed
             Service status is: Started
             Service startup is: Automatic
             IPSec service is available, but no policy is assigned or active
             Note: run “ipseccmd /?” for more detailed information
         The command completed successfully




Using the netstat Command
         Using the Netstat command displays a variety of statistics about a
         computer’s active TCP/IP connections. It’s a useful tool to use when you’re
         having trouble with TCP/IP applications, such as File Transfer Protocol
         (FTP), HyperText Transport Protocol (HTTP), and so on.
                                      Using the netstat Command          379

Displaying connections
If you run netstat without specifying any parameters, you get a list of
active connections, something like this:

C:\>netstat
Active Connections
  Proto Local Address   Foreign Address                 State
  TCP    Doug:1463      192.168.168.10:1053             ESTABLISHED
  TCP    Doug:1582      192.168.168.9:netbios-ssn       ESTABLISHED
  TCP    Doug:3630      192.168.168.30:9100             SYN_SENT
  TCP    Doug:3716      192.168.168.10:4678             ESTABLISHED
  TCP    Doug:3940      192.168.168.10:netbios-ssn      ESTABLISHED
C:\>

This list shows all the active connections on the computer and indicates the
local port used by the connection, as well as the IP address and port number
for the remote computer.

You can specify the -n switch to display both local and foreign addresses in
numeric IP form:

C:\>netstat -n
Active Connections
  Proto Local Address           Foreign Address       State
  TCP    192.168.168.21:1463    192.168.168.10:1053   ESTABLISHED
  TCP    192.168.168.21:1582    192.168.168.9:139     ESTABLISHED
  TCP    192.168.168.21:3658    192.168.168.30:9100   SYN_SENT
  TCP    192.168.168.21:3716    192.168.168.10:4678   ESTABLISHED
  TCP    192.168.168.21:3904    207.46.106.78:1863    ESTABLISHED
  TCP    192.168.168.21:3940    192.168.168.10:139    ESTABLISHED
C:\>

Finally, you can specify the -a switch to display all TCP/IP connections and
ports that are being listened to. I won’t list the output from that command
here because it would run several pages, and I want to do my part for the
rainforests. Suffice it to say that it looks a lot like the netstat output shown
previously, but a lot longer.

                                                                                    Book IV
Displaying interface statistics                                                    Chapter 6
If you use an -e switch, netstat displays various protocol statistics, like           TCP/IP Tools and
this:
                                                                                        Commands



C:\>netstat -e
Interface Statistics
                                   Received                Sent
Bytes                             672932849           417963911
Unicast packets                     1981755             1972374
Non-unicast packets                  251869               34585
Discards                                  0                   0
Errors                                    0                   0
Unknown protocols                      1829
C:\>
380   Using the netstat Command


         The items to pay attention to in this output are the Discards and Errors.
         These numbers should be zero, or at least close to it. If they’re not, the
         network may be carrying too much traffic or the connection may have a
         physical problem. If no physical problem exists with the connection, try
         segmenting the network to see whether the error and discard rates drop.

         You can display additional statistics by using an -s switch, like this:

         C:\>netstat -s

         IPv4 Statistics

           Packets Received                              =   9155
           Received Header Errors                        =   0
           Received Address Errors                       =   0
           Datagrams Forwarded                           =   0
           Unknown Protocols Received                    =   0
           Received Packets Discarded                    =   0
           Received Packets Delivered                    =   14944
           Output Requests                               =   12677
           Routing Discards                              =   0
           Discarded Output Packets                      =   71
           Output Packet No Route                        =   0
           Reassembly Required                           =   0
           Reassembly Successful                         =   0
           Reassembly Failures                           =   0
           Datagrams Successfully Fragmented             =   0
           Datagrams Failing Fragmentation               =   0
           Fragments Created                             =   0

         IPv6 Statistics

           Packets Received                              =   3
           Received Header Errors                        =   0
           Received Address Errors                       =   0
           Datagrams Forwarded                           =   0
           Unknown Protocols Received                    =   0
           Received Packets Discarded                    =   0
           Received Packets Delivered                    =   345
           Output Requests                               =   377
           Routing Discards                              =   0
           Discarded Output Packets                      =   0
           Output Packet No Route                        =   0
           Reassembly Required                           =   0
           Reassembly Successful                         =   0
           Reassembly Failures                           =   0
           Datagrams Successfully Fragmented             =   0
           Datagrams Failing Fragmentation               =   0
           Fragments Created                             =   0

         ICMPv4 Statistics
                               Using the netstat Command   381

                            Received        Sent
  Messages                  6               14
  Errors                    0               0
  Destination Unreachable   6               14
  Time Exceeded             0               0
  Parameter Problems        0               0
  Source Quenches           0               0
  Redirects                 0               0
  Echo Replies              0               0
  Echos                     0               0
  Timestamps                0               0
  Timestamp Replies         0               0
  Address Masks             0               0
  Address Mask Replies      0               0
  Router Solicitations      0               0
  Router Advertisements     0               0

ICMPv6 Statistics

                            Received        Sent
  Messages                  3               7
  Errors                    0               0
  Destination Unreachable   0               0
  Packet Too Big            0               0
  Time Exceeded             0               0
  Parameter Problems        0               0
  Echos                     0               0
  Echo Replies              0               0
  MLD Queries               0               0
  MLD Reports               0               0
  MLD Dones                 0               0
  Router Solicitations      0               6
  Router Advertisements     3               0
  Neighbor Solicitations    0               1
  Neighbor Advertisements   0               0
  Redirects                 0               0
  Router Renumberings       0               0
                                                                  Book IV
TCP Statistics for IPv4
                                                                 Chapter 6
  Active Opens                          =   527                     TCP/IP Tools and
  Passive Opens                         =   2
  Failed Connection Attempts            =   1
                                                                      Commands



  Reset Connections                     =   301
  Current Connections                   =   1
  Segments Received                     =   8101
  Segments Sent                         =   6331
  Segments Retransmitted                =   301

TCP Statistics for IPv6

  Active Opens                          = 1
  Passive Opens                         = 1
382   Using the nslookup Command


           Failed Connection Attempts                   =   0
           Reset Connections                            =   1
           Current Connections                          =   0
           Segments Received                            =   142
           Segments Sent                                =   142
           Segments Retransmitted                       =   0

         UDP Statistics for IPv4

           Datagrams Received          =   6703
           No Ports                    =   0
           Receive Errors              =   0
           Datagrams Sent              =   6011

         UDP Statistics for IPv6

           Datagrams Received          =   32
           No Ports                    =   0
           Receive Errors              =   0
           Datagrams Sent              =   200
         C:\>



Using the nslookup Command
         The nslookup command is a powerful tool for diagnosing DNS problems.
         You know you’re experiencing a DNS problem when you can access a
         resource by specifying its IP address but not its DNS name. For example, if
         you can get to www.ebay.com by typing 66.135.192.87 in your browser’s
         address bar but not by typing www.ebay.com, you have a DNS problem.


         Looking up an IP address
         The simplest use of nslookup is to look up the IP address for a given DNS
         name. For example, how did I know that 66.135.192.87 was the IP address
         for ebay.com? I used nslookup to find out:

         C:\>nslookup ebay.com
         Server: ns1.orng.twtelecom.net
         Address: 168.215.210.50
         Non-authoritative answer:
         Name:    ebay.com
         Address: 66.135.192.87
         C:\>

         As you can see, just type nslookup followed by the DNS name you want to
         look up. Nslookup issues a DNS query to find out. This DNS query was sent
         to the server named ns1.orng.twtelecom.net at 168.215.210.50. It
         then displayed the IP address that’s associated with ebay.com: namely,
         66.135.192.87.
                                                    Using the nslookup Command               383


                               Get me out of here!
One of my pet peeves is that it seems as if every   exiting the program and returning to a
program that uses subcommands chooses a             command prompt:
different command to quit the application. I
                                                    Quit        Sayonara
can never remember whether the command
to get out of nslookup is quit, bye, or             Exit        Ciao
exit. I usually end up trying them all. And no
matter what program I’m using, I always seem        Bye         Mañana
to choose the one that works for some other         Leave       Makelikeatree
program first. When I’m in nslookup, I
use bye first. When I’m in FTP, I try exit
first. Arghh! If I were King of the Computer        Of course, the final command to try would be
Hill, every program that had subcommands            Andgetouttahere (in honor of Biff from
would respond to the following commands by          the Back to the Future movies).




           In some cases, you may find that using an nslookup command gives you the
           wrong IP address for a host name. To know that for sure, of course, you have
           to know with certainty what the host IP address should be. For example, if
           you know that your server is 203.172.182.10 but Nslookup returns a
           completely different IP address for your server when you query the server’s
           host name, something is probably wrong with one of the DNS records.


           Using nslookup subcommands
           If you use nslookup without any arguments, the nslookup command
           enters a subcommand mode. It displays a prompt character (>) to let you
           know that you’re in nslookup subcommand mode rather than at a normal
           Windows command prompt. In subcommand mode, you can enter various
           subcommands to set options or to perform queries. You can type a question
           mark (?) to get a list of these commands. Table 6-2 lists the subcommands                    Book IV
           you’ll use most.                                                                            Chapter 6
                                                                                                          TCP/IP Tools and
                                                                                                            Commands


              Table 6-2        The Most Commonly Used nslookup Subcommands
             Subcommand                 What It Does
             name                       Queries the current name server for the specified name.
             server name                Sets the current name server to the server you specify.
             root                       Sets the root server as the current server.
                                                                                         (continued)
384   Using the nslookup Command



           Table 6-2 (continued)
           Subcommand           What It Does
           set type=x           Specifies the type of records to be displayed, such as A,
                                CNAME, MX, NS, PTR, or SOA. Specify ANY to display all
                                records.
           set debug            Turns on Debug mode, which displays detailed information
                                about each query.
           set nodebug          Turns off Debug mode.
           set recurse          Enables recursive searches.
           set norecurse        Disables recursive searches.
           exit                 Exits the nslookup program and returns you to a
                                command prompt.



         Displaying DNS records
         One of the main uses of nslookup is to examine your DNS configuration to
         make sure that it’s set up properly. To do that, follow these steps:

         1. At a command prompt, type nslookup without any parameters.
            nslookup displays the name of the default name server and displays
            the > prompt.
                  C:\>nslookup
                  Default Server: ns1.orng.twtelecom.net
                  Address: 168.215.210.50
                  >
         2. Type the subcommand set type=any.
            nslookup silently obeys your command and displays another prompt:
                  > set type=any
                  >
         3. Type your domain name.
            nslookup responds by displaying the name servers for your domain:
                  > lowewriter.com
                  Server: ns1.orng.twtelecom.net
                  Address: 168.215.210.50
                  Non-authoritative answer:
                  lowewriter.com nameserver = NS000.NS0.com
                  lowewriter.com nameserver = NS207.PAIR.com
                  lowewriter.com nameserver = NS000.NS0.com
                  lowewriter.com nameserver = NS207.PAIR.com
                  >
                                 Using the nslookup Command          385

4. Use a server command to switch to one of the domain’s name servers.
    For example, to switch to the first name server listed in Step 3, type
    server NS000.NS0.com. nslookup replies with a message that indicates
    the new default server:
       > server ns000.ns0.com
       Default Server: ns000.ns0.com
       Address: 216.92.61.61
       >
5. Type your domain name again.
    This time, nslookup responds by displaying the DNS information for
    your domain:
       > lowewriter.com
       Server: ns000.ns0.com
       Address: 216.92.61.61
       lowewriter.com
               primary name server = ns207.pair.com
               responsible mail addr = root.pair.com
               serial = 2001121009
               refresh = 3600 (1 hour)
               retry   = 300 (5 mins)
               expire = 604800 (7 days)
               default TTL = 3600 (1 hour)
       lowewriter.com nameserver = ns000.ns0.com
       lowewriter.com nameserver = ns207.pair.com
       lowewriter.com MX preference = 50, mail exchanger =
          sasi.pair.com
       lowewriter.com internet address = 209.68.34.15
       >
6. Type exit to leave the Nslookup program.
    You return to a command prompt.
       > exit
       C:\>
                                                                                Book IV
Wasn’t that fun?                                                               Chapter 6
                                                                                  TCP/IP Tools and
Locating the mail server for an e-mail address
                                                                                    Commands



If you’re having trouble delivering mail to someone, you can use nslookup
to determine the IP address of the user’s mail server. Then, you can use the
ping command to see whether you can contact the user’s mail server. If not,
you can use the tracert command to find out where the communication
breaks down.

To find a user’s mail server, start nslookup and enter the command set
type=MX. Then, enter the domain portion of the user’s e-mail address.
For example, if the user’s address is Doug@LoweWriter.com, enter
386   Using the nslookup Command


         LoweWriter.com. nslookup will display the MX (Mail eXchanger) information
         for the domain, like this:

         C:\>nslookup
         Default Server: ns7.attbi.com
         Address: 204.127.198.19
         > set type=mx
         > lowewriter.com
         Server: ns7.attbi.com
         Address: 204.127.198.19
         lowewriter.com MX preference = 50, mail exchanger = sasi.pair.com
         lowewriter.com nameserver = ns000.ns0.com
         lowewriter.com nameserver = ns207.pair.com
         ns000.ns0.com    internet address = 216.92.61.61
         ns207.pair.com internet address = 209.68.2.52
         >

         Here, you can see that the name of the mail server for the LoweWriter.com
         domain is sasi.pair.com.


         Taking a ride through DNS-Land
         Ever find yourself wondering how DNS really works? I mean, how is it that
         you can type a DNS name like www.disneyland.com into a Web browser
         and you’re almost instantly transported to the Magic Kingdom? Is it really
         magic?

         Nope. It isn’t magic; it’s DNS. In Book IV, Chapter 4, I present a somewhat dry
         and theoretical overview of DNS. After you have the nslookup command in
         your trusty TCP/IP toolbox, take a little trip through the Internet’s maze of
         DNS servers to find out how DNS gets from www.disneyland.com to an IP
         address in just a matter of milliseconds.

         DNS does its whole name resolution thing so fast, it’s easy to take it for granted.
         If you follow this little procedure, you’ll gain a deeper appreciation for what DNS
         does literally tens of thousands of times every second of every day.

         1. At a command prompt, type nslookup without any parameters.
             nslookup displays the name of the default name server and displays
             the > prompt.
                 C:\>nslookup
                 Default Server: ns1.orng.twtelecom.net
                 Address: 168.215.210.50
                 >
         2. Type root to switch to one of the Internet’s root servers.
             nslookup switches to one of the Internet’s 13 root servers and then
             displays the > prompt.
                 > root
                 Default Server: A.ROOT-SERVERS.NET
                 Address: 198.41.0.4
                                 Using the nslookup Command           387

3. Type www.disneyland.com.
   nslookup sends a query to the root server to ask if it knows the IP address
   of www.disneyland.com. The root server answers with a referral,
   meaning that it doesn’t know about www.disneyland.com, but you should
   try one of these servers because they know all about the com domain.
      > www.disneyland.com
      Server: A.ROOT-SERVERS.NET
      Address: 198.41.0.4
      Name:    www.disneyland.com
      Served by:
      - A.GTLD-SERVERS.NET
                 192.5.6.30
                 com
      - G.GTLD-SERVERS.NET
                 192.42.93.30
                 com
      - H.GTLD-SERVERS.NET
                 192.54.112.30
                 com
      - C.GTLD-SERVERS.NET
                 192.26.92.30
                 com
      - I.GTLD-SERVERS.NET
                 192.43.172.30
                 com
      - B.GTLD-SERVERS.NET
                 192.33.14.30
                 com
      - D.GTLD-SERVERS.NET
                 192.31.80.30
                 com
      - L.GTLD-SERVERS.NET
                 192.41.162.30
                 com
      - F.GTLD-SERVERS.NET
                 192.35.51.30
                 com                                                              Book IV
      - J.GTLD-SERVERS.NET                                                       Chapter 6
                 192.48.79.30
                 com
                                                                                    TCP/IP Tools and
      >
                                                                                      Commands



4. Type server followed by the name or IP address of one of the com
   domain name servers.
   It doesn’t really matter which one you pick. nslookup switches to that
   server. (The server may spit out some other information besides what
   I’ve shown here; I left it out for clarity.)
      > server 192.48.79.30
      Default Server: [192.5.6.30]
      Address: 192.5.6.30
      >
388   Using the nslookup Command


         5. Type www.disneyland.com again.
             nslookup sends a query to the com server to ask whether it knows
             where the Magic Kingdom is. The com server’s reply indicates that it
             doesn’t know where www.disneyland.com is, but it does know which
             server is responsible for disneyland.com.
                Server: [192.5.6.30]
                Address: 192.5.6.30
                Name:    www.disney.com
                Served by:
                - huey.disney.com
                          204.128.192.10
                          disney.com
                - huey11.disney.com
                          208.246.35.40
                          disney.com
                >
             Doesn’t it figure that Disney’s name server is huey.disney.com? There’s
             probably also a dewey.disney.com and a louie.disney.com.
         6. Type server followed by the name or IP address of the second-level
             domain name server.
             nslookup switches to that server:
                > server huey.disney.com
                Default Server: huey.disney.com
                Address: 204.128.192.10
                >
         7. Type www.disneyland.com again.
             Once again, nslookup sends a query to the name server to find out
             whether it knows where the Magic Kingdom is. Of course, huey.
             disney.com does know, so it tells us the answer:
                > www.disneyland.com
                Server: huey.disney.com
                Address: 204.128.192.10
                Name:    disneyland.com
                Address: 199.181.132.250
                Aliases: www.disneyland.com
                >
         8. Type Exit, and then shout like Tigger in amazement at how DNS
             queries work.
             And be glad that your DNS resolver and primary name server do all this
             querying for you automatically.

         Okay, maybe that wasn’t an E Ticket ride, but it never ceases to amaze me
         that the DNS system can look up any DNS name hosted anywhere in the
         world almost instantly.
                                         Using the pathping Command            389

Using the pathping Command
      pathping is an interesting command that’s unique to Windows. It’s sort of
      a cross between the ping command and the tracert command, combining
      the features of both into one tool. When you run pathping, it first traces
      the route to the destination address much the way tracert does. Then,
      it launches into a 25-second test of each router along the way, gathering
      statistics on the rate of data loss to each hop. If the route has a lot of hops,
      this can take a long time. However, it can help you to spot potentially
      unreliable hops. If you’re having intermittent trouble reaching a particular
      destination, using pathping may help you pinpoint the problem.

      The following command output is typical of the pathping command. (Using
      an -n switch causes the display to use numeric IP numbers only, instead of
      DNS host names. Although fully qualified host names are convenient, they
      tend to be very long for network routers, which makes the pathping output
      very difficult to decipher.)

      C:\>pathping -n www.lowewriter.com
      Tracing route to lowewriter.com [209.68.34.15]
      over a maximum of 30 hops:
        0 192.168.168.21
        1 66.193.195.81
        2 66.193.200.5
        3 168.215.55.173
        4 168.215.55.101
        5 168.215.55.77
        6 66.192.250.38
        7 66.192.252.22
        8 208.51.224.141
        9 206.132.111.118
       10 206.132.111.162
       11 64.214.174.178
       12 192.168.1.191
       13 209.68.34.15
      Computing statistics for 325 seconds...
                                                                                          Book IV
                Source to Here   This Node/Link
                                                                                         Chapter 6
      Hop RTT Lost/Sent = Pct Lost/Sent = Pct Address
        0                                        192.168.168.21                             TCP/IP Tools and
                                    0/ 100 = 0%   |
                                                                                              Commands


        1   1ms    0/ 100 = 0%      0/ 100 = 0% 66.193.195.81]
                                    0/ 100 = 0%   |
        2   14ms 0/ 100 = 0%        0/ 100 = 0% 66.193.200.5
                                    0/ 100 = 0%   |
        3   10ms 0/ 100 = 0%        0/ 100 = 0% 168.215.55.173
                                    0/ 100 = 0%   |
        4   10ms 0/ 100 = 0%        0/ 100 = 0% 168.215.55.101
                                    0/ 100 = 0%   |
        5   12ms 0/ 100 = 0%        0/ 100 = 0% 168.215.55.77
                                    0/ 100 = 0%   |
        6   14ms 0/ 100 = 0%        0/ 100 = 0% 66.192.250.38
                                    0/ 100 = 0%   |
390   Using the ping Command


           7    14ms    0/ 100 =    0%       0/   100   = 0%    66.192.252.22
                                             0/   100   = 0%     |
           8    14ms    0/ 100 =    0%       0/   100   = 0%    208.51.224.141
                                             0/   100   = 0%     |
           9    81ms    0/ 100 =    0%       0/   100   = 0%    206.132.111.118
                                             0/   100   = 0%     |
          10    81ms    0/ 100 =    0%       0/   100   = 0%    206.132.111.162]
                                             0/   100   = 0%     |
          11    84ms    0/ 100 =    0%       0/   100   = 0%    64.214.174.178]
                                             0/   100   = 0%     |
          12    --- 100/ 100 =100%         100/   100   =100%   192.168.1.191
                                             0/   100   = 0%     |
          13   85ms 0/ 100 =        0%       0/   100   = 0%    209.68.34.15
         Trace complete.



Using the ping Command
         ping is probably the most basic TCP/IP command line tool. Its main purpose
         is to determine whether you can reach another computer from your computer.
         It uses Internet Control Message Protocol (ICMP) to send mandatory
         ECHO_REQUEST datagrams to the specified host computer. When the reply
         is received back from the host, the ping command displays how long it took
         to receive the response.

         You can specify the host to ping by using an IP address, as in this example:

         C:\>ping 192.168.168.10
         Pinging 192.168.168.10 with 32 bytes of data:
         Reply from 192.168.168.10: bytes=32 time<1ms TTL=128
         Reply from 192.168.168.10: bytes=32 time<1ms TTL=128
         Reply from 192.168.168.10: bytes=32 time<1ms TTL=128
         Reply from 192.168.168.10: bytes=32 time<1ms TTL=128
         Ping statistics for 192.168.168.10:
              Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
         Approximate round trip times in milli-seconds:
              Minimum = 0ms, Maximum = 0ms, Average = 0ms
         C:\>

         By default, the ping command sends four packets to the specified host. It
         displays the result of each packet sent. Then it displays summary statistics:
         how many packets were sent, how many replies were received, the error
         loss rate, and the approximate round-trip time.

         You can also ping by using a DNS name, as in this example:

         C:\>ping www.lowewriter.com
         Pinging lowewriter.com [209.68.34.15] with 32 bytes of data:
         Reply from 209.68.34.15: bytes=32 time=84ms TTL=53
         Reply from 209.68.34.15: bytes=32 time=84ms TTL=53
         Reply from 209.68.34.15: bytes=32 time=84ms TTL=53
                                             Using the route Command           391

      Reply from 209.68.34.15: bytes=32 time=84ms TTL=53