Idea of Cisco Router Interfaces

Router Interfaces

Interface configuration is one of the most important configuration of the router.Without interfaces, the router is useless. Interfaces configurations must be exact to communicate with other devices. Some of the configurations used to configure an interface are Network layer addresses, mediatype, bandwidth, and other administrator commands.

Example:

Figure: Cisco Router

Router (config) # int   ethernet  ?

<0-0> Ethernet interface  number

Router (config) # int ethernet  0

Router (config-if)#

Router (config) # int  serial  ?

<0-0> serial interface number

Router (config) # int  serial  1

Router (config)-if)#

Bringing Up an Interface

You can turn an interface off the interface command shutdown or turn it on with the no shutdown command. If an interface is shutdown, it will display administratively down when using the show interface command, and the show running-config command will show the interface as shut down. All interfaces are shut down by default.

Router #sh  int  e0

Ethernet 0 is administratively down, line protocol is down

[output cut]

Bring up an interface with the no shutdown command.

Router #config   t

Enter configuration  commands,one per line.End with

CNTL/Z

Router (config)# int  e0

Router (config-if)# no  shutdown

Router (config-if)#^Z

00:57:08: %LINK-3-UPDOWN:Interface Ethernet 0,changed State to up

00:57:09: % LINEPROTO-5-UPDOWN: Line protocol on interface Ethernet 0,changed state to up

Router #sh  int  e0

Ethernet0 is up,line protocol is up.