Both ASBR1 and ASBR2 advertise defaults into the network, expecting to have the capability to route to the Internet through BGP-learned routes. In this case, ASBR2 is already up, fully converged. However, if ASBR1 reloads, when it comes back up, OSPF is likely to converge faster than BGP. As a result, ASBR1 will advertise its default route, and OSPF routers may send packets to ASBR1, but ASBR1 will end up discarding the packets until BGP converges.

Using the stub router feature on the ASBRs solves the problem by making them advertise infinite metric routes (cost 16,777,215) for any transit routes—either for a configured time period or until BGP convergence is complete. To do so, under router ospf, the ASBRs would use either the maxmetric router-lsa on-startup announce-time command or the max-metric router-lsa on-startup wait-for-bgp command. With the first version, the actual time period (in seconds) can be set. With the second, OSPF waits until BGP signals that convergence is complete or until 10 minutes pass, whichever comes first.