In the topology in Figure 1, all of the routers have been configured to support OSPF routing.

A quick look at the R1 routing table (Figure 2) reveals that it receives default route information, the R2 LAN ( and the link between R2 and R3 ( However, it does not receive the R3 LAN OSPF route.

The output in Figure 3 verifies the OSPF settings on R3. Notice that R3 only advertises the link between R3 and R2. It does not advertise the R3 LAN (

For an interface to be enabled for OSPF, a matching network command must be configured under the OSPF routing process. The output in Figure 4 confirms that the R3 LAN is not advertised in OSPF.

The example in Figure 5 adds a network command for the R3 LAN. R3 should now advertise the R3 LAN to its OSPF neighbors.

The output in Figure 6 verifies that the R3 LAN is now in the routing table of R1.