This form of the command has no arguments.
Purpose: To enable OSPF to advertise the default route 0.0.0.0 into the OSPF domain. This form of the command will only advertise the default route if the route exists in the local IP routing table.
Initial Cisco IOS Software Release: 10.0
Configure the routers in Figure 4-1 as shown in the following code.
Figure 4-1. When OSPF Advertises a Default Route the Advertising Router Becomes an Autonomous System Border Router (ASBR)
Router A interface Loopback0