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cisco router configuration basics


Title: cisco router configuration basics Author: ken Last modified by: ymbk Created Date: 6/15/1997 3:20:46 PM Document presentation format: On-screen Show – PowerPoint PPT presentation

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Date added: 17 December 2018
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Title: cisco router configuration basics

cisco router configuration basics
  • router configuration controls the operation of
    the router
  • interface address and netmask
  • routing information (static or dynamic)
  • booting and startup information
  • security (passwords)

  • configuration statements have different contexts
  • global
  • enable-password mysecret
  • interface
  • interface ethernet0
  • ip address
  • router
  • router ospf 1
  • network area 0

global configuration
  • global configuration statements are independent
    of any particular interface or routing protocol,
  • hostname myrouter
  • enable-password mysecret
  • service password-encryption
  • logging facility local0
  • logging

global configuration
  • ip-specific global configuration statements
  • ip classless
  • static route creation
  • ip route

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

interface configuration
  • ip address and netmask configuration, using
    interface commands (interactive configuration
    example, showing prompts)
  • routerconfig terminal
  • router(config)interface e0
  • router(config-if)ip address
  • router(config-if)no shutdown
  • router(config-if)Z
  • router

There are two modes on a cisco router
  • normal mode
  • routergt
  • enable mode
  • routergt enable
  • router config terminal

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

where is the configuration?
  • router always has two configurations
  • running configuration
  • in RAM, determines how the router is currently
  • 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

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

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

changing the configuration
  • configuration statements can be entered
    interactively at the console, or in a telnet
  • 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

interactive configuration
  • can use direct serial connection to console port,
  • telnet to vtys (virtual terminals), or
  • modem connection to aux port
  • in every case, changes are made (almost)
    immediately, to the running configuration

interactive configuration
  • enter configuration mode, using configure term
  • prompt gives a hint about where you are
  • routerconfigure 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

storing the configuration on a host
  • requires tftpdon a unix host destination file
    must exist before the file is written and must be
    world writable...
  • copy run tftp
  • K-rtrcopy 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

restoring the configuration from a host
  • use tftp to pull file from unix host, copying
    to running config or startup
  • K-rtrcopy tftp start
  • Address of remote host
  • Name of configuration file K-rtr-confg?
  • Configure using K-rtr-confg from
  • Loading K-rtr-confg from (via
    Ethernet0) !
  • OK - 1005/128975 bytes
  • OK
  • K-rtr reload

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?
  • ltpartial commandgt ? lists all possible
    subcommands, e.g.
  • routershow ?
  • routershow ip ?

getting help
  • ltpartial commandgt? shows all possible command
  • routercon?
  • configure connect
  • this is different (space before ?)
  • routerconf ?
  • 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
  • ltcrgt

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

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
  • ltcrgt
  • router(config-if)ip addr
  • router(config-if)

getting lazy help
  • TAB character will complete a partial word
  • router(config)intltTABgt
  • router(config)interface etltTABgt
  • router(config)interface ethernet 0
  • router(config-if)ip addltTABgt
  • router(config-if)ip address ...
  • not really necessary partial commands can be
  • routerconf t
  • router(config)int e0
  • router(config-if)ip addr 195.176...

getting lazy
  • command history
  • IOS maintains short list of previously typed
  • up-arrow or P recalls previous command
  • down-arrow or N recalls next command
  • line editing
  • left-arrow, right-arrow moves cursor inside
  • D or backspace will delete character in front
    of cursor