OSPF LSA Types
Not-So-Stubby-Area (NSSA)
- Don’t propagate Type 5 LSA. So an ASBR can’t be a part of a stub area.
- Sometimes, though, there is limited need to import external routes into an area, which is where the NSSA’s that allow an ASBR to take part in an area, are useful.
- Rather than have the ASBR send out a Type 5 LSA, it will send out a Type 7 NSSA External LSA.
- Type 7 LSA can’t be advertised into another OSPF area. So, the ABR in the NSSA gets the Type 7 LSA and translates it into a Type 5 LSA.
- The Type 5 LSA is then allowed to flood the OSPF AS.