Interface configuration is one of the most important router configurations because without interfaces, a router is pretty much a completely useless object. Plus, interface configurations must be totally precise to enable communication with other devices. Network layer addresses, media type, bandwidth, and other administrator commands are all used to configure an interface.
Different routers use different methods to choose the interfaces used on them. For instance, the following command shows a Cisco router with 10 serial interfaces, labeled 0 through 9:
Router(config)#int serial ?
<0-9> Serial interface number
Now it’s time to choose the interface you want to configure. Once you do that, you will be in interface configuration ...