Cisco Router Interfaces

To make changes to an interface, you use the interface command from global configuration mode:

Router(config)#interface ?
Async	Async interface
BVI	Bridge-Group Virtual Interface
CTunnel	CTunnel interface
Dialer	Dialer interface
FastEthernet	FastEthernet IEEE 802.3
Group-Async	Async Group interface
Lex	Lex interface
Loopback	Loopback interface
MFR	Multilink Frame Relay bundle interface
Multilink	Multilink-group interface
Null	Null interface
Serial	Serial Interface
Tunnel	Tunnel interface
Vif	PGM Multicast Host interface
Virtual-Template	Virtual Template interface
Virtual-TokenRing	Virtual TokenRing Interface
range	interface range command

Router(config)#interface fastethernet 0/0
Router(config-if)#

Did you notice that the prompt changed to Router(config-if)#? This tells you that you’re in interface configuration mode. And wouldn’t it be nice if the prompt also gave you an indication of what interface you were configuring? Well, at least for now we’ll have to live without the prompt information, because it doesn’t.