How to put an IP address on an Ethernet interface

There are 4 easy steps to accomplish this task.  Remember that you will always need to access the global configuration mode to add interfaces. Let’s walk through these steps together.

First you should connect to your router. You would do this with the enable command.
router> enable            enter

Now we need to access the configurator to use the terminal.
router# config t            enter                 (Note: t for terminal)

Notice that the prompt changes as you go deeper into the router configuration. (> sign changes to # sign).

You should see the following message:
Enter configuration commands, one per line.  End with CNTL/Z.

Next we need to configure the Ethernet interface.
router(config)# interface Ethernet 0/0    enter

Notice that the prompt now changes to (config-if)# indicating that we are now in configuration interface mode.

The final step is to type the IP address and subnet for the ethernet interface.
router(config-if)# ip address 1.1.1.1 255.255.255.0

Pressing CNTL/Z saves your changes and gets you back to the enable prompt. Of course you will want to verify your configuration. Type the following command at the enable prompt:
router# show interface Ethernet 0/0   enter

You should see the Ethernet 0/o is up and the IP address that we configured is displayed.