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cisco router configuration basics

cisco router configuration basics. overview. router configuration controls the operation of the router: interface address and netmask routing information (static or dynamic) booting and startup information security (passwords). overview. configuration statements have different contexts:

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cisco router configuration basics

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  1. cisco router configuration basics

  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)

  3. overview • configuration statements have different contexts: • global: • enable-password mysecret • interface: • interface ethernet0 • ip address 195.176.118.254 255.255.255.0 • router: • router ospf 1 • network 195.176.118.0 0.0.0.255 area 0

  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 195.176.118.42

  5. global configuration • ip-specific global configuration statements: • ip classless • static route creation: • ip route 195.176.118.0 255.255.248.0 195.176.31.1

  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

  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 195.176.118.254 255.255.255.0 router(config-if)#no shutdown router(config-if)#^Z router#

  8. There are two modes on a cisco router • normal mode • router> • enable mode • router> enable • router# config terminal

  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

  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

  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 run start • copy run tftp • copy start tftp • copy tftp start • copy flash start • copy start flash

  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

  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

  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

  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 195.176.118.253 255.255.255.0 • K-rtr(config-if)#no shutdown • use the no command to nullify command given: • (config-if)# no ip addr 195.176.118.253 255.255.255.0

  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 []? 195.176.118.42 • 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 195.176.118.42? [confirm] • Building configuration... • Writing /usr/local/tftpd/K-rtr-confg !![OK]

  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 [255.255.255.255]? 195.176.118.42 • Name of configuration file [K-rtr-confg]? • Configure using K-rtr-confg from 195.176.118.42? [confirm] • Loading K-rtr-confg from 195.176.118.42 (via Ethernet0): ! • [OK - 1005/128975 bytes] • [OK] • K-rtr# reload

  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 ?

  19. getting help • “<partial command>?” shows all possible command completions • router#con? • configure connect • this is different (space before “?”): • router#conf ? • memory Configure from NV memory • network Configure from a TFTP network host • overwrite-network Overwrite NV memory from TFTP... network host • terminal Configure from the terminal • <cr>

  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 address

  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 169.222.64.1 ? • A.B.C.D IP subnet mask • router(config-if)#ip addr 169.222.64.1 255.255.255.0 ? • secondary Make this IP address a secondary address • <cr> • router(config-if)#ip addr 169.222.64.1 255.255.255.0 • router(config-if)#

  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 ... 195.176.118.1 255.255.255.0 • not really necessary; partial commands can be used: • router#conf t • router(config)#int e0 • router(config-if)#ip addr 195.176...

  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

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