Propagating a Default Static Route
With OSPF, the router connected to the Internet is used to propagate a default route to other routers in the OSPF routing domain. This router is sometimes called the edge, the entrance, or the gateway router. However, in OSPF terminology, the router located between an OSPF routing domain and a non-OSPF network is also called the autonomous system boundary router (ASBR).
In Figure 1, R2 is single-homed to a service provider. Therefore, all that is required for R2 to reach the Internet is a default static route to the service provider.
Note: In this example, a loopback interface with IP address 209.165.200.225 is used to simulate the connection to the service provider.
To propagate a default route, the edge router (R2) must be configured with:
- A default static route using the ip route 0.0.0.0 0.0.0.0 {ip-address | exit-intf} command.
- The default-information originate router configuration mode command. This instructs R2 to be the source of the default route information and propagate the default static route in OSPF updates.
Figure 2 shows how to configure a fully-specified default static route to the service provider.