Routers and TCP_IP Networking

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					                                 Routers and TCP/IP Networking
                                 March 9 (Day); March 23 (Night)

   Routers:
           o   A router is a multiport connectivity device that directs nodes on a network.
               Basically, when a router receives an incoming packet, it reads the packet’s
               network address and subnet mask and determines to which network the packet
               should be delivered.
           o   A router’s strength lies in its intelligence. Not only can routers keep track of the
               locations of certain nodes on the network, but they can also determine the
               shortest path between two nodes.
           o   They can do the following:
                      Connect dissimilar networks.
                      Interpret Layer 3 addressing and other information (such as quality of
                       service indicators).
                      Determine the best path for data to follow from point A to point B.
                      Reroute traffic if a primary path is down but another path is available.


           o   Directing Data:
                      Static routing is a technique in which a network administrator programs
                       a router to use specific paths between node.
                                Static routing does not take into account for occasional network
                                 congestion, failed connections, or device moves.
                                Moving a device of part of the network causes the network
                                 administrator to reprogram the router.
                      Dynamic routing automatically calculates the best path between two
                       nodes and accumulates this information in a routing table.
                                If congestion of failures affect the network, a router using
                                 dynamic routing can detect the problems and reroute data
                                 through a different path.
                                When a router is added to a network, the routing table is updated.


                      The best path refers to the most efficient route from one node on a
                       network to another. Some routers determine best path by fewest number
                       of hops. Others use complex mathematical algorithms.
   Configuring TCP/IP:
           o   For a PC to access the Internet, it must have the TCP/IP protocol loaded (p. 378).
           o   TCP/IP is so popular that even non-Internet accessible Internets are using it (p.
               378).
           o   In Windows 98/ME, you configure TCP/IP though Network Neighborhood.
               Windows 200/XP, you configure TCP/IP in My Network Places.


   TCP/IP Commands:
           o   Ping – a command that enables one machine to check whether it can
               communicate with another machine (p. 384).
           o   Winipcfg – a tool in Windows 9X/ME that displays the TCP/IP settings and
               information (p. 384).
           o   Ipconfig – a tool in Windows NT/2000/XP that displays the TCP/IP settings and
               information (p. 384).
           o   Tracert – a tool that shows the route data takes to reach its destination (p. 385).


   Private Network Addresses:
           o   There is a standard reserved block of addresses for use in private networks.
               These are networks that will never be connected directly to any other public
               network.
           o   The private networking standard is shown below:
                          Network Class                        Address
                                                                Range
                          10.0.0.0 – 10.255.255.255               A
                          172.16.0.0 – 172.31.255.255             B
                          192.168.0.0 – 192.168.255.255           C
           o   Routers on the Internet are designed not to “route” private network addresses. If
               a router encounters a data packet destined for a private network, it simply drops
               it. This is the reason why private network addresses are also called “non-
               routable” addresses.
           o   In short, the basic purpose of private networks is to allow companies to establish
               LANs without the cost or bother of acquiring public IP addresses.
   Default Gateway:
           o   A computer that wants to send data to another machine outside its local area
               network cannot know all the IP addresses on the Internet (p. 382).
           o   Instead, all IP addresses know the name of one computer, to which they pass all
               the data they need to send outside the LAN (p. 383).
           o   This machine is called the default gateway, and it is usually the local router (p.
               382).

				
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