One of the main elements to configure on a Cisco router is its interfaces. The router is usually equipped with Ethernet interfaces (for LAN connectivity) or Serial/ATM/T1/E1 interfaces for WAN connectivity. Below you will find three typical router interface configuration scenarios to get an idea about this important setup.

Configuring Ethernet or Fast Ethernet Interfaces
Router> enable
Router # config terminal

! enter the interface configuration submode
Router(config) # interface fastethernet 0/0

! IP configured on the interface
Router(config-if) # ip address 10.1.10.1 255.255.255.0

!bring the interface up
Router (config-if) # no shutdown
Router (config-if) # description lan (assign a name to the interface)
Router (config-if) # exit
Router (config) #

* Note that the interface naming can be different. Examples are FastEthernet, Ethernet, GigabitEthernet etc. Also, the interface numbering varies from router to router, such as 0, 1, 0/0 0/1, etc.

Configuring DTE Serial Interfaces
Note that DTE serial interfaces receive clock from the Serial WAN modem.

Router> enable
Router# config terminal

! enter the interface configuration submode
Router (config) # interface serial 0/0

Router (config-if) # ip address 172.16.1.1 255.255.255.252
Router (config-if) # no shutdown
Router (config-if) # description WAN Network (assign a name to the interface)
Router (config-if) # exit
Router (config) #

* Note that the interface numbering can be 0, 1, 0/0 0/1, etc. This varies by router.

Configuring DCE Serial Interfaces
Note that DCE serial interfaces provide clock to the connected device on the interface.

Router> enable
Router# config terminal
Router(config) # interface serial 0 / 1
Router(config-if) # ip address 10.1.1.1 255.255.255.0

!configure the clock rate that will be provided by the router
Router(config-if) # clock rate 128000
Router(config-if) # no shutdown
Router(config-if) # description WAN Network (assign a name to the interface)
Router(config-if) # exit
Router(config) #

* Note that the interface number can be 0, 1, 0/0 0/1, etc. This varies by router model.

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