Basic Cisco IOS Tutorial
÷What is Cisco IOS ?
Cisco IOS (Internetwork Operating System) is an OS used by majority of Cisco routers and switches (older switch used Cat OS). The first IOS was written by William Yeager and Gami Tumambing.
Cisco IOS has a CLI (command line interface) characteristics. It has two major mode, privileged and normal mode.
In privileged mode you can configure the router and the normal mode is used for checking the configuration.
Basic Configuration
To enter the privileged mode enter the following command.
Router>enable
Router#
Note the hash at the end of the router hostname Router#. This means the router is in privileged mode.
Before configuring anything, you have to enter the configuration mode.
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#
Note the prompt changed to "Router(config)#". This is the configuration mode for Cisco IOS.
At anytime if you want to check what command is available under certain mode, you can use "?" to list all the commands available
Router(config)#?
Configure commands:
aaa Authentication, Authorization and Accounting.
aal2-profile Configure AAL2 profile
access-list Add an access list entry
alarm-interface Configure a specific Alarm Interface Card
alias Create command alias
alps Configure Airline Protocol Support
appfw Configure the Application Firewall policy
appletalk Appletalk global configuration commands
application Define application
....
Now to change the host name of the router, enter hostname command under config mode.
Router(config)#hostname R1
R1(config)#
Note that the command prompt is changed to R1 to reflect the new host name
Saving the Configuration
Cisco IOS is designed to save all these changes in RAM. So in case if you mess up something, you can just reload the router, and get everything back the the way it was.
Once you are satisfied with it, you can save the configuration to the permanent storage (NVRAM). First you have to exit the config mode, and then run the commands.
R1(config)#exit
R1#
*Mar 1 00:35:42.031: %SYS-5-CONFIG_I: Configured from console by console
R1#copy running-config startup-config
Destination filename [startup-config]?
Building configuration...
[OK]
R1#
Thats it for this tutorial. Stay tuned for the next one.