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  • 1. cisco router configuration basics cisco router configuration NTW2000 / track 2 # 1
  • 2. overview router configuration controls the operation of the router: interface address and netmask routing information (static or dynamic) booting and startup information security (passwords) cisco router configuration NTW2000 / track 2 # 2
  • 3. overview configuration statements have different contexts: global: enable-password mysecret interface: interface ethernet0 ip address cisco router configuration router: router ospf 1 network area 0 NTW2000 / track 2 # 3
  • 4. global configuration global configuration statements are independent of any particular interface or routing protocol, e.g.: hostname myrouter enable-password mysecret service password-encryption logging facility local0 logging cisco router configuration NTW2000 / track 2 # 4
  • 5. global configuration ip-specific global configuration statements: ip classless static route creation: ip route cisco router configuration NTW2000 / track 2 # 5
  • 6. interface configuration interfaces are named by type and position; e.g.: ethernet0, ethernet1,... ethernet5 serial0, serial1 ... serial3 and can be abbreviated: ethernet0 or eth0 or e0 serial0 or ser0 or s0 cisco router configuration NTW2000 / track 2 # 6
  • 7. interface configuration ip address and netmask configuration, using interface commands (interactive configuration example, showing prompts): router#config terminal router(config)#interface e0 router(config-if)#ip address router(config-if)#no shutdown router(config-if)#^Z router# cisco router configuration NTW2000 / track 2 # 7
  • 8. There are two modes on a cisco router normal mode router> enable mode router> enable router# config terminal cisco router configuration NTW2000 / track 2 # 8
  • 9. interface configuration administratively enable/disable the interface router(config-if)#no shutdown router(config-if)#shutdown (config-if)# no ip proxy-arp (config-if)# no ip directed broadcast (config-if)# no ip redirect description #description 128k circuit 123-ABC to hotel cisco router configuration NTW2000 / track 2 # 9
  • 10. where is the configuration? router always has two configurations: running configuration in RAM, determines how the router is currently operating is changed by using the configuration command to see it: show running startup configuration in NVRAM, determines how the router will operate after next reload is changed using the copy command to see it: show startup cisco router configuration NTW2000 / track 2 # 10
  • 11. where is the configuration? can also be stored in more permanent places: external hosts, using TFTP to move it around in flash memory in the router copy command is used to move it around copy copy copy copy copy copy cisco router configuration run start run tftp start tftp tftp start flash start start flash NTW2000 / track 2 # 11
  • 12. looking at the configuration use “show running-configuration” to see the current configuration use “show startup-configuration” to see the configuration in NVRAM, that will be loaded the next time the router is rebooted or reloaded cisco router configuration NTW2000 / track 2 # 12
  • 13. changing the configuration configuration statements can be entered interactively at the console, or in a telnet session, or, edited in a text file and uploaded to the router at a later time; some configuration statements, especially access lists, are very difficult to work with interactively, so editing and uploading the file is the only practical way to work; also allows version control and auditing changes cisco router configuration NTW2000 / track 2 # 13
  • 14. interactive configuration can use direct serial connection to console port, or telnet to vty’s (“virtual terminals”), or modem connection to aux port in every case, changes are made (almost) immediately, to the running configuration cisco router configuration NTW2000 / track 2 # 14
  • 15. interactive configuration enter configuration mode, using “configure term” prompt gives a hint about where you are: router#configure terminal router(config)#hostname K-rtr K-rtr(config)#ip classless K-rtr(config)#ip subnet-zero K-rtr(config)#interface ethernet3 K-rtr(config-if)#ip address K-rtr(config-if)#no shutdown use the no command to nullify command given: (config-if)# no ip addr cisco router configuration NTW2000 / track 2 # 15
  • 16. storing the configuration on a host requires: `tftpd’on a unix host; destination file must exist before the file is written and must be world writable... copy run tftp K-rtr#copy run tftp Remote host []? Name of configuration file to write [K-rtr-confg]? /usr/local/tftpd/K-rtr-confg Write file /usr/local/tftpd/K-rtr-confg on... host [confirm] Building configuration... Writing /usr/local/tftpd/K-rtr-confg !![OK] cisco router configuration NTW2000 / track 2 # 16
  • 17. restoring the configuration from a host use ‘tftp’ to pull file from unix host, copying to running config or startup K-rtr#copy tftp start Address of remote host []? Name of configuration file [K-rtr-confg]? Configure using K-rtr-confg from [confirm] Loading K-rtr-confg from (via Ethernet0): ! [OK - 1005/128975 bytes] [OK] K-rtr# reload cisco router configuration NTW2000 / track 2 # 17
  • 18. getting help IOS has a built-in help facility; use “?” to get a list of possible configuration statements “?” after the prompt lists all possible commands: router#? “<partial command> ?” lists all possible subcommands, e.g.: router#show ? router#show ip ? cisco router configuration NTW2000 / track 2 # 18
  • 19. getting help “<partial command>?” shows all possible command completions router#con? configure connect this is different (space before “?”): router#conf ? memory network host overwrite-network terminal <cr> cisco router configuration Configure from NV memory Configure from a TFTP network Overwrite NV memory from TFTP.. network host Configure from the terminal NTW2000 / track 2 # 19
  • 20. getting help this also works in configuration mode: router(config)#ip a? accounting-list accounting-threshold accounting-transits address-pool alias as-path router(config)#int e0 router(config-if)#ip a? access-group accounting cisco router configuration address NTW2000 / track 2 # 20
  • 21. getting help can “explore” a command to figure out the syntax: router(config-if)#ip addr ? A.B.C.D IP address router(config-if)#ip addr ? A.B.C.D IP subnet mask router(config-if)#ip addr ? secondary Make this IP address a secondary address <cr> router(config-if)#ip addr router(config-if)# cisco router configuration NTW2000 / track 2 # 21
  • 22. getting lazy help TAB character will complete a partial word router(config)#int<TAB> router(config)#interface et<TAB> router(config)#interface ethernet 0 router(config-if)#ip add<TAB> router(config-if)#ip address ... not really necessary; partial commands can be used: router#conf t router(config)#int e0 router(config-if)#ip addr 195.176... cisco router configuration NTW2000 / track 2 # 22
  • 23. getting lazy command history IOS maintains short list of previously typed commands up-arrow or ‘^P’ recalls previous command down-arrow or ‘^N’ recalls next command line editing left-arrow, right-arrow moves cursor inside command ‘^D’ or backspace will delete character in front of cursor cisco router configuration NTW2000 / track 2 # 23