Final answer:
To configure OSPF in area 0 on a router, two commands are needed: 'router ospf 1' to start the OSPF process and 'network [network-address] [wildcard-mask] area 0' to specify the participating networks and associate them with area 0.
Step-by-step explanation:
When configuring a router to route within OSPF area 0, you must enter specific commands in the router's command-line interface (CLI). There are two primary configuration commands needed to set up OSPF for a given network.
First, enter OSPF router configuration mode with the command:
RouterA(config)# router ospf 1
Second, define the network(s) that will participate in OSPF, including their area, with the network command:
RouterA(config-router)# network [network-address] [wildcard-mask] area 0
For instance, to include all interfaces on the 192.168.1.0 network with a subnet mask of 255.255.255.0 in area 0, you would use:
RouterA(config-router)# network 192.168.1.0 0.0.0.255 area 0
The command router ospf 1 starts OSPF on the router, and the '1' is simply the process ID, which is locally significant. The network command specifies which interfaces or networks should participate in OSPF routing, and the area 0 indicates that they belong to area 0, which is the OSPF backbone area.