OSPF Stub Router Advertisement
A. Retana, L. Nguyen, R. White, A. Zinin, D. McPherson · 2001
This memo describes a backward-compatible technique that may be used by OSPF (Open Shortest Path First) implementations to advertise unavailability to forward transit traffic or to lower the preference level for the paths through such a router.In some cases, it is desirable not to route transit traffic via a specific OSPF router.However, OSPF does not specify a standard way to accomplish this. MotivationIn some situations, it may be advantageous to inform routers in a network not to use a specific router as a transit point, but still route to it.Possible situations include the following.o The router is in a critical condition (for example, has very high CPU load or does not have enough memory to store all LSAs or build the routing table ).o Graceful introduction and removal of the router to/from the network.o Other (administrative or traffic engineering) reasons.