OSPF LSA AND AREA TYPES

OSPF LSA TYPES

LSA type 1 – Router LSA’s (Generated by each router)

LSA type 2 – Network LSA’s (Generated by DR)

LSA type 3 – Summary LSA’s (Generated by an ABR)

LSA type 4 – Summary LSA’s which advertises path to an ASBR to reach external networks. (Generated by an ABR)

LSA type 5 – External LSA’s which advertises external routes from another routing domain (Generated by an ASBR)

LSA type 7 – NSSA LSA, which allows an ASBR inside an OSPF stubby area, which will get converted to LSA type 5 at nearest ABR

OSPF AREA TYPES

1) Stub Areas – Allow only LSA type 1, 2 and 3 to propogate.

2) Totally Stub Areas – Allow only LSA type 1 and 2 to propogate. The ABR will inject a Defualt Route to the routers inside Totally Stub area.

3) NSSA Areas – Same as Stub, but allow LSA type 7 also to propogate. These type 7 LSA’s will get converted to type 5 LSA’s at nearest ABR.

4) Totally NSSA Areas – Same as Totally Stub areas, but allow LSA type 7 also to propogate. These type 7 LSA’s will get converted to type 5 LSA’s at nearest ABR. The ABR also will inject a Defualt Route to the routers inside Totally NSSA area.

5) Normal Areas - An area in which routers are connected usually, which allows all types of LSA.

6) Backbone Area - An area which connects two normal area , where all LSA's are supported