Objective: To understand how to enable interfaces on a router and what it takes for the
interface to be UP.
Lab Equipment: We will be using Router 1 & Router 2. To select Router 1 click on the
button labeled "Router1" located at the top of the screen.
1. On Router 1, enter global configuration mode
Router>enableRouter#conf tRouter(config)#Router(config)#hostname Router1
2. We now wish to configure the Ethernet Interface. To do so, we must enter interface
configuration mode. Type the command to enter interface configuration mode for
Ethernet 0.
Router1(config)#interface Ethernet 0Router1(config-if)#
3. What can you do to view all the commands available to you in interface configuration
user mode?
Just type a '?' by itself.
this will show you all the available commands for that mode.
Router1(config-if)#?
4. Which command listed, looks like it would disable or turn off the interface?
shutdown Shutdown the selected interface
5. We can often do the opposite of a command, by typing no in front of it. What
command might enable this interface? Execute this command on Router 1 Ethernet 0 to
enable the interface.
Router1(config-if)#no shutdown
6. Now add a description for this interface.
Router1(config-if)#description Ethernet interface on Router 1
7. To view your interface description exit back to privilege mode and do a show interface
command. You should see your description under Ethernet 0.
Router1(config-if)#endRouter1#show interface
8. Now connect to Router 2 and enter the Ethernet 0 interface.
Router#conf tRouter(config)#hostname Router2Router2(config)#interface Ethernet 0
9. Now enable the interface.
Router2(config-if)#no shutdown
10. Now that the interfaces on both sides of our Ethernet connection are enabled you
should be able to see one another by CDP. Use the command show cdp neighbors to view
all directly connected Cisco Routers.
Router2(config-if)#end
Router2#show cdp neighbors
Configuring the Interfaces
If an interface is administratively down. You must enter configuration mode, then enter
interface configuration mode, and lastly, issue the command no shutdown.
Router#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#interface ethernet 0Router(config-if)#no shutdownRouter(config-if)#
%LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0, changed state to up
%LINK-3-UPDOWN: Interface Ethernet0, changed state to up
Router(config-if)#endRouter#
If your interface is the DCE, you must provide clocking using the clock rate command.
Router#config t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#interface serial 0Router(config-if)#clock rate 56000Router(config-if)#endRouter#
It is often useful to put a description of what the interface is used for using the description
command.
Router#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#int e0Router(config-if)#description My Connection to the Engineering HubRouter(config-if)#endRouter#
You can view your changes using show running-config or show interfaces or show controllers
