How to configure OSPF Totally NSSA Area

This topic is to discuss the following lesson:

Hi Rene !

When you configured the area 1 nssa no-summary you have not configured the same statement in router Susan. Why not ? Its not also necessary? or i am misunderstanding and you have to configured in the ASBR only ?

You said that we have to configured the area 1 nssa-summary in all the area. So i have that doubt.

THANKS IN ADVANCE !!

Hi Ieltxu,

Good question. You have to configure “no-summary” only on the ABR since that’s the router that will inject the default route(s) into the area. No need to do it on all routers in the (totally) NSSA area.

Rene

Rene lets say i have 3 routers on Area 1, to have a totally NSSA, i only need to configure area 1 stub nssa on 3 routers? then the abr is area 1 stub nssa no-summary?
so in short, the ASBR must be configured “area 1 nssa” while the ABR is “area 1 nssa no-summary” to achieve the Totally NSSA?

Hi John,

That’s right, within the NSSA area all routers only need “area x nssa”. Only the ABR requires “area x nssa no-summary”.

Rene

Hi Rene

So can we say that for Stub and NSSA user needs to configure in all the nodes in Area that the area type is stub or nssa but in case of Totally Stub or Totally NSSA it is enough if it is configured only in ABR. Am I right ?

Hi Ajith,

That’s right, it’s the ABR that will block the LSAs from entering the stub or nssa area so that’s the only router where you have to add “no-summary”.

Rene