Quick Guide - Managing A Cisco Internetwork

Document Sample
Quick Guide - Managing A Cisco Internetwork Powered By Docstoc

Quick Guide - Managing A Cisco Internetwork
Managing a Cisco Internetwork - Cisco Router Components -- Bootstrap, POST, ROM Monitor (all in ROM); Mini-IOS (RXBOOT, or bootloader), RAM, ROM, Flash, NVRAM, Configuration register. - Cisco Router Boot Sequence -- POST; Bootstrap loads the IOS; the IOS loads a configuration ("startup-config", if present in NVRAM). - Configuration register -- 16 bits, read 15-0 from left to right. Default is 0x2102 = 0010 0001 0000 0010 -- load IOS from flash and look for "startup-config". - Configuration register common values in bits (and hex): - 0-3 -- 0x0000-0x000F -- Boot field, as follows: - 00 -- ROM monitor mode -- register = 2100. You must manually boot the router with the "b" command. - 01 -- Boot image from ROM -- register = 2101. - 02-F -- Specifies a default boot filename. - 6 -- 0x0040 -- ignore NVRAM contents. - 7 -- 0x0080 -- OEM bit enabled. - 8 -- 0x0100 -- Break disabled. - 10 -- 0x0400 -- IP broadcast with all zeros. - 11-12 -- 0x0800-0x1000 -- console line speed. - 13 -- 0x2000 -- Boot default ROM software if network boot fails. - 14 -- 0x4000 -- IP broadcasts do not have net numbers. - 15 -- 0x8000 -- Enable diagnostic messages and ignore NVM contents. - "sh version" shows the current value of the configuration register. - Change the config register (run this from "config t" mode) -- "config-register 0x0101" -Boot into ROM mode and then show the current config register value. - Recovering Passwords: - Perform a "break" while the router boots -- you should see "rommon 1 >". - "confreg 0x2142" -- turns on bit 6 -- ignore NVRAM contents. Note: On a Cisco 2500 router, type "o" after the break, then "o/r 0x2142". ! To boot from a different file, use "boot system ", or "boot system tftp ". - Reboot the router -- "reset" ("I" on a 2500 -- meaning "initialize"). - Fix password and reboot -- "copy start run", "config t", "enable secret ", "config-register 0x2102", Ctrl-Z, "copy run start", "reload". - Back up and Restore the Cisco IOS: - Check the flash and the TFTP server -- "sh flash", "ping". - Backup the IOS image -- "copy flash tftp". - Restore of Upgrade the Cisco Router IOS -- "copy tftp flash" (you may be asked to erase existing flash data). You can also erase it manually with "erase flash:". - Set up a Cisco router to be a TFTP server -- "config t", "tftp-server flash:." - Back up or Restore the Cisco Configuration -- "copy run tftp", "copy tftp run". Erase the startup config -- "erase start". - Cisco Discovery Protocol (CDP) -- collect hardware and protocol information about neighbor devices. "sh cdp" shows CDP values: - CDP timer -- how often CDP packets are transmitted to all active interfaces (default 60 seconds) -- "config t", "cdp timer 90". - CDP holdtime -- how long to hold packets received from neighbor devices (default 180 seconds) -- "config t", "cdp holdtime 240". - "sh cdp nei" (or "show cdp neighbor") shows CDP information ONLY about directly connected devices. "sh cdp neighbor detail" = "sh cdp entry *" BOTH display extended information ("sh cdp entry *" does NOT work on a 1900 switch). - "sh cdp traffic" shows CDP traffic summary. "sh cdp interface" shows interface CDP information. - CDP is enabled by default. Disable globally -- "no cdp run". To disable per interface -"config t", "int s0", "no cdp enable". - "telnet" = "" -- "telnet" can be skipped, it is assumed. - Connect via telnet to several routers simultaneously -- "telnet", "Ctrl-Shift-6 then x" (suspend), "telnet". - "sh sessions" shows telnet connections from your router to another device. "sh users" shows telnet sessions in your router. - "disconnect " disconnects a session. "clear line " disconnects a telnet session in your router. - Use a host table to resolve addresses -- "config t", "ip host myrouter". Then you can telnet via "telnet myrouter", or just "myrouter". Remove with "no ip host myrouter". - Using a DNS server for name resolution -- "config t", "ip domain-lookup", "ip name-server", "ip domain-name". - "sh hosts" displays the host table, or DNS information, if set up. - "ping" and "traceroute" can be used from user mode and enable mode, but not from config mode. - If you try to run traceroute with IPX or AppleTalk, you will get an error. Those two are not supported yet.

By badboy

Description: CCNA Exam, Exam Answers, the network, ccna test, Module 2, Module 8, Certification Exam Preparation, Free Resources, Packet Tracer, cisco ccna training, Module 3, IP address, Module 4, Module 5, subnet mask, Quick Notes, IP address, in the Frame, encapsulation type, Frame Relay header, the Frame, Inverse ARP, Relay switch, error checking, Associate Exam, Leading the way, Best Practice, CCNA Exam, virtual circuits, Cisco Certified Network Associate, IP access, filter packets, Free Cisco,