Chabot College
ELEC 99.08
IOS Configuration Commands
CISCO NETWORKING ACADEMY
Configuration Topics
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Configuration file
Ways to enter a config file to the router
IOS configuration commands
Additive editing
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Configuration File
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•
•
Just a text file
Text instructions are interpreted by the EXEC.
Loaded to RAM
Changes in the config file take place
instantaneously. No reboot or other process is
required.
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Configuration File
• Commands may be entered in any order; the
IOS will place the commands in the correct
position in the config file.
• Editing is additive. More about this later...
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Config may be entered from
• NVRAM This is the default at reload or cold start.
– rtr#config memory
– rtr#copy start run
• Setup Mode dialog
– rtr#setup
• TFTP server
– rtr#config network
– rtr#copy tftp run
• Terminal (con0, aux0, vty0 4)
– rtr#config terminal
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Also:
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Review: Which mode is this?
• oak(config)#
• Global configuration mode
Used for:
– General configuration commands
– Static routes
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Review: Which mode is this?
• oak(config-if)#
• Interface configuration mode
Used for:
– Setting IP addresses and subnet masks
– Setting other interface characteristics
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Review: Which mode is this?
• oak(config-router)#
• Router configuration mode
Used for:
– Setting routing protocols
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Review: Which mode is this?
• oak(config-line)#
• Line configuration mode
Used for:
– Setting login passwords on lines:
• con 0
• aux 0
• vty 0 4
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Global, Interface, Line & Router Modes
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Global Config Commands
• hostname
– name of router
– format: one word, no spaces
– changes instantaneously
rtr#conf t
rtr(config)#hostname oak
oak(config)#banner motd $Router Admin: J. Jones$
oak(config)#ip route 0.0.0.0 0.0.0.0 s1
oak(config)#enable password cisco
oak(config)#enable secret chabot
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Global Config Commands
• banner motd
– message of the day (shown at login)
– format: repeated character delimits message
– in example below, $ is delimiter
rtr#conf t
rtr(config)#hostname oak
oak(config)#banner motd $Router Admin: J. Jones$
oak(config)#ip route 0.0.0.0 0.0.0.0 s1
oak(config)#enable password cisco
oak(config)#enable secret chabot
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Global Config Commands
• ip route
– defines a “static” route
– format: ip route x.x.x.x (address) y.y.y.y (mask) interface
– in example below, the “default route” is set
rtr#conf t
rtr(config)#hostname oak
oak(config)#banner motd $Router Admin: J. Jones$
oak(config)#ip route 0.0.0.0 0.0.0.0 s1
oak(config)#enable password cisco
oak(config)#enable secret chabot
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Global Config Commands
• enable passwword
– sets the weak “enable” password
– format: enable password [word]
rtr#conf t
rtr(config)#hostname oak
oak(config)#banner motd $Router Admin: J. Jones$
oak(config)#ip route 0.0.0.0 0.0.0.0 s1
oak(config)#enable password cisco
oak(config)#enable secret chabot
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Global Config Commands
• enable secret
– sets the encrypted “enable secret” password
– format: enable secret [word]
– once entered, will not be readable in config file
rtr#conf t
rtr(config)#hostname oak
oak(config)#banner motd $Router Admin: J. Jones$
oak(config)#ip route 0.0.0.0 0.0.0.0 s1
oak(config)#enable password cisco
oak(config)#enable secret chabot
CISCO NETWORKING ACADEMY
Global Config Commands
• no ip domain-lookup
– turns off DNS lookups
– format: no ip domain lookup
– useful in lab, where there is no DNS
rtr#conf t
rtr(config)#hostname oak
oak(config)#banner motd $Router Admin: J. Jones$
oak(config)#ip route 0.0.0.0 0.0.0.0 s1
oak(config)#enable password cisco
oak(config)#enable secret chabot
oak(config)#no ip domain-lookup
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Global Config - Practice
• Try it now with Router e-Sim:
• Enter global config mode.
• Enter the following commands:
router>en
router#conf t
router(config)#hostname hayward
hayward(config)#banner motd $Administered by(yourname)$
hayward(config)#enable password cisco
hayward(config)#enable secret chabot
hayward(config)#exit
hayward#exit
• then log in again, and note the motd and passwords
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Global config: changing to Interface Config
• interface ethernet 0
– selects the interface to be configured
– format: int e0 (substitute s0, s1, or e1 as appropriate)
– prompt gives no indication of the current interface
being configured.
oak#conf t
oak(config)#int e0
oak(config-if)#
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Interface Config Commands
• ip address
– sets ip address & subnet mask
– format: ip address x.x.x.x (address) y.y.y.y (mask)
oak#conf t
oak(config)#int e0
oak(config-if)#ip address 192.168.4.1 255.255.255.0
oak(config-if)#
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Interface Config Commands
• descripton
– comment to describe the interface
– format: desc [text text text]
oak#conf t
oak(config)#int e0
oak(config-if)#ip address 192.168.4.1 255.255.255.0
oak(config-if)#desc Oakland LAN
oak(config-if)#
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Interface Config Commands
• no shutdown
– brings up an interface that was
administratively shut down
– format: no shut
oak#conf t
oak(config)#int e0
oak(config-if)#ip address 192.168.4.1 255.255.255.0
oak(config-if)#desc Oakland LAN
oak(config-if)#no shut
oak(config-if)#
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Interface Config Commands
• exit
– returns to Global Config mode
– format: exit
oak#conf t
oak(config)#int e0
oak(config-if)#ip address 192.168.4.1 255.255.255.0
oak(config-if)#desc Oakland LAN
oak(config-if)#no shut
oak(config-if)#exit
oak(config)#
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Interface Config - Practice
• Try it now with Router e-Sim:
• show interface e0 and note:
– is the interface UP and UP?
– is an IP address shown?
• Enter interface config mode for Ethernet 0.
• Enter the following commands:
hayward(config)#int eo
hayward(config-if)#ip address 192.168.3.1 255.255.255.0
hayward(config-if)#desc This is the Hayward LAN
hayward(config-if)#no shut
hayward(config)#exit
hayward#exit
• then show int e0 and note the effects of your configuration
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Global config: changing to Line Config
• line con 0
– selects the line to be configured
– format: line vty 0 4 (substitute con 0 or aux 0 as appropriate)
– prompt gives no indication of the current line being
configured.
oak#conf t
oak(config)#line con 0
oak(config-line)#
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Line Config Commands
• login
– enables password control for login
– format: login
oak#conf t
oak(config)#line con 0
oak(config-line)login
oak(config-line)#
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Line Config Commands
• password
– defines the password for this line
– format: password [word]
oak#conf t
oak(config)#line con 0
oak(config-line)login
oak(config-line)#password cisco
oak(config-line)#
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Line Config Commands
• exit
– returns to Global Config mode
– format: exit
oak#conf t
oak(config)#line con 0
oak(config-line)login
oak(config-line)#password cisco
oak(config-line)#exit
oak(config)#
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Line Config - Practice
• Try it now with Router e-Sim:
• show run and note whether there are passwords on line con 0,
aux 0, and vty 0
• Enter line config mode for con 0.
• Enter the following commands:
Notice
the
change
here
hayward(config)#line con 0
hayward(config-line)#login
hayward(config-line)#password cisco
hayward(config-line)#line vty 0 4
hayward(config-line)#login
hayward(config-line)#password cisco
hayward(config-line)#exit
hayward#^Z
• then show run and note the effects of your configuration
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Additional Line Config Command
• logging synchronous
– prevents system messages from interrupting
your typing input in the middle of a line
– add to console line
– format: logging synchronous
oak#conf t
oak(config)#line con 0
oak(config-line)logging synchronous
oak(config-line)#
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Additional Line Config Command
• logging synchronous
– Router e-Sim doesn’t understand this
command, so you can’t practice with it.
– Useful in in your real config files.
oak#conf t
oak(config)#line con 0
oak(config-line)login
oak(config-line)#password cisco
oak(config-line)logging synchronous
oak(config-line)#
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Global config: changing to Router Config
• router rip
– selects the dynamic routing protocol
– format: router [protocol] (rip or igrp as appropriate)
oak#conf t
oak(config)#router rip
oak(config-router)#
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Router Config Commands
• network
– sets the networks on which the protocol will
send and receive updates
– format: network x.x.x.x
oak#conf t
oak(config)#router rip
oak(config-router)#network 192.168.4.0
oak(config-router)#network 10.0.0.0
oak(config-router)#
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Router Config Commands
• exit
– returns to Global Config mode
– format: exit
oak#conf t
oak(config)#router rip
oak(config-router)#network 192.168.4.0
oak(config-router)#network 10.0.0.0
oak(config-router)#exit
oak(config)#
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Router Config - Practice
• Try it now with Router e-Sim:
• show run and note whether RIP has been set as the dynamic
routing protocol
• Enter line router config mode
• Enter the following commands:
hayward(config)#router rip
hayward(config-router)#network 10.0.0.0
hayward(config-router)#network 192.168.3.0
hayward(config-router)#exit
hayward(config)#exit
hayward#exit
• then show run and note the effects of your configuration
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“No” Commands
• To remove or reverse any command, type
the command again, preceded by no
oak#conf t
oak(config)#no router rip
oak(config)#
CISCO NETWORKING ACADEMY
“No” Command - Practice
• Try it now with Router e-Sim:
• show run and note whether RIP has been set as the dynamic
routing protocol
• Enter global config mode
• Enter the following commands:
hayward(config)#no router rip
hayward(config)#exit
hayward#sh ru
• then show run and note whether RIP has been deleted
CISCO NETWORKING ACADEMY
“No” Command - Practice
• Earlier, you set the ethernet 0
– IP address and subnet mask
– description
• Now try using the no command to remove them.
• Answer:
hayward(config)#int e0
hayward(config-if)#no ip address
hayward(config-if)#no desc
hayward(config-if)#exit
hayward(config)#exit
hayward#sh ru
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Additive Editing
• New commands add to the file and replace like
commands only.
• Other commands remain in the config.
• Even if you load an entire config file to RAM,
old commands not included in the new config
file will remain in RAM.
• Confusion and problems can result.
• Principle: Start clean to be sure:
– erase start, reload
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Additive Editing - Results of Loading a Config on Top of a Current Config
2. New Config
Loaded from
NVRAM or TFTP
!
hostname oakland
!
enable password cisco
!
!
!
ip route 0.0.0.0 0.0.0.0 s1
!
no router rip
+
1. Current
Running Config
in RAM
!
hostname hayward
!
enable password cisco
!
banner motd $Shutdown 4PM$
!
!
!
router rip
=
3. Resulting
Running Config
in RAM
!
hostname oakland
!
enable password cisco
!
banner motd $Shutdown 4PM$
!
ip route 0.0.0.0 0.0.0.0 s1
!
!
Whatthe
Will
will
resulting
be the resulting
config include
hostname?
enable
apassword?
rip
banner
static
routing?
ipmotd?
route?
CISCO NETWORKING ACADEMY