Cisco - Router - Assign an IP address

Check state of the available interfaces

show ip interface brief

do show ip interface brief

Configure FastEthernet0/0:

interface FastEthernet 0/0
ip address 192.168.1.1 255.255.255.0
no shut

returns:

#
%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up

NOTE:

interface FastEthernet 0/0: Enters configuration mode of port FastEthernet 0/0 (FE0/0).
ip address: Adds IP address to port FE0/0.
no shut. (or no shutdown) brings FE0/0 from down (offline) state to up (online).

do show ip interface brief

NOTE: This should show the Port is up with address that was assigned.

interface fastethernet0/0
no ip address

shutdown