Assigning interfaces to an area
Once you define OSPFv2 areas, you can assign interfaces to the areas. All device ports must be assigned to one of the defined areas on an OSPFv2 device. When a port is assigned to an area, all corresponding subnets on that port are automatically included in the assignment.
To assign a loopback interface to an area with the IP address of 10.5.0.0, perform the following task:
The following example assigns a loopback interface to an area with the IP address of 10.5.0.0.
device# configure terminal device(config)# interface loopback 2 device(config-lbif-2)# ip ospf area 10.5.0.0