Interface Configuration - IOS

SummaryTo modify the configuration parameters of a specific interface, for example, the IP address, a user must enter the interface configuration mode. The interface configuration mode for a nework interface, which is entered from the global configuration mode, is entered by typing the keyword interface followed by the interface name. 
Interface Configuration 
The following is an example of configuring a router with a 10 Mbps Ethernet interface card with two ports that is located in slot 0 of the router, with names Fa0/0 and Fa0/1. The following commands configure port 0 with IP address and port 1 with IP address
Router1# configure terminal
Router1 (config)# no ip routing
Router1 (config)# ip routing
Router1 (config)# interface Fa0/0
Router1 (config-if)# no shutdown
Router1 (config-if)# ip address
Router1 (config-if)# interface Fa0/1
Router1 (config-if)# no shutdown
Router1 (config-if)# ip address
Router1 (config-if)# end
The following list summarizes the IOS commands for enabling IP forwarding and for configuring IP addresses:
ip routing
      -Enables IP forwarding
no ip routing
      -Disables IP forwarding. Deletes the content of the routing table.
no shutdown          
      -Enables network interface
      -Disables a network interface
ip address IP address netmask            
      -Sets the IP address and netmask of an interface to IPaddress and netmask 
Configuration ModeThe interface configuration mode for the network interface on port 1 of a 10 Mbps Ethernet card inserted in slot 0 of the router is entered with the command
Router1(config)# interface Fa0/1
The command prompt of the interface configuration mode is
To return to the global configuration mode, one types
Router1(config-if)# exit
When a global configuration command is typed in the interface configuration mode, then IOS changes to the global configuration command.
Configuration & Other Information The following list contains useful commands for displaying information about the router:     
write term     
show running-config          
      -Displays the current configuration of the router. The two commands produce identical results.
 show config
show startup-config             
      -Displays the startup configuration of the router. The two commands produce identical results.
      -Forces a reboot of IOS. Diiscards the running configuration and reloads the startup configuration.
copy running-config starting-config 
      -Saves the current configuration as the startup configuration. The new startup configuration will be used the next time IOS     is rebooted.
show version
      -Displays the version of IOS.
 show protocols
      -Displays the IP configuration of the interfaces of the router. Indicates if IP forwarding is enabled or disabled.
 show ip route
      -Displays the routing table.
 show ip cache
      -Displays the routing cache,
show interfaces
show interfaces interfacename
      -Displays information about all network interfaces. When an interface name is given as argument, for example, Fa0/1,   information is displayed only for the specified interface.
 show ip arp
      -Displays the contencts of the ARP cache.