Cisco Networking: Interface Configuration Mode
Configuring Cisco network devices requires that you enter the Global Configuration mode, but one of the variations in this mode is Interface Configuration. When you are working with Global Configuration mode, you may enter an interface for configuration or any number of subconfiguration modes.
At that point in time, any commands you type apply only to the interface. When you are in Interface Configuration mode, your prompt looks something like this, while other configuration prompts will vary slightly in the displayed text:
Each interface or subconfiguration mode has its own list of configuration commands. Here are some of the commands that you see on a network interface:
arp: Sets an interface ARP type or timeout.
cdp: Configures CDP for a specific interface.
delay: Specifies the delay on interface throughput. This is useful for limiting throughput or for simulating slower connections in a lab.
description: Sets a descriptive name for the interface.
exit: Exits Interface mode and returns to Configuration mode.
ip: Configures IP protocol on the interface.
logging: Configures logging for the interface.
media-type: Chooses a media type for interfaces that have the option.
mtu: Sets the interface maximum transmission unit (MTU), which limits the size of the Ethernet frame.
no: Negates other commands that have been issued.
shutdown: Disables or shuts down the interface.
Type the exit command to leave a mode and move to the next higher mode. You need to do that if the commands you want to use do not work at that level. For example, to view the current configuration that is in use, use the show running-configuration command. That command can be used only in Privileged EXEC mode, so if you are in Global Configuration mode, you need to move one level up to use that command.
If after viewing the running configuration, you decide that you need to change the IP address of the Fast/Ethernet0/0 interface of a router, you need to use a sequence like this (do not worry about the actual commands at this point:
Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#interface FastEthernet 0/0 Router(config-if)#ip address 192.168.1.2 255.255.255.0 Router(config-if)#exit Router(config)#exit Router#