OSPF Areas question

Unanswered Question

hi all

I quick question which I cant seem to find a clear answer for.

I was considering implementing stub or totally stub areas in my network, but one area in particular has a small RIP network attached ( this RIP network will not produce a default route ).

As far as I can see the choice of area type will effect LSAs ingressing into the area, thus if I make the area with this RIP network a totally stub.

inside the area I will have a default to the backbone ( area 0 ), any intra area routes as well as the routes from the ASBR with the RIP network?

and these external LSA will be propagated out towards the backbone?

What is normally done in this type of scenario?

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Edison Ortiz Sat, 10/06/2007 - 08:16

Will the ASBR participate in the stub area ? If so, you will need to implement NSSA (not-so-stubby area) instead of stub or totally stub areas.

You can't redistribute external routes into a stub or totally stub area.

You also have to think about the inter-area routes. Do you want the ASBR or ABR to handle those ? How many areas are you planning to implement ?

To give an accurate account on how to proceed, I highly recommend you post with a topology diagram from your network.

sundar.palaniappan Sat, 10/06/2007 - 08:54

As the name states NSSA Totally Stub Area is nothing but NSSA + Totally Stub Area.

Since the original poster wants the intra-area routes + External RIP route advertised towards the backbone from this stub area it warrants the use of NSSA. Moreover the original poster just wants to allow only default route into the stub (NSSA) area. But NSSA would allow type 3 LSAs and making the area as NSSA TSA wouldn't allow the type 3 LSAs except the default route LSA. With NSSA TSA the ABR would just inject a type 3 default route LSA and also translate the RIP (type 7 LSA) to type 5 LSA to any non-stub OSPF area it's connected to.



Edison Ortiz Sat, 10/06/2007 - 09:02


I understand the OSPF area differences, however - I don't understand the point you are trying to make with this reply.

sundar.palaniappan Sat, 10/06/2007 - 09:13


There's no point here to be made except both are trying to provide a solution to the original poster's concern. I suggest configuring NSSA Totally Stub Area and you propose NSSA. I explain the reason why NSSA TSA is required and NSSA alone doesn't suffice in this scenario. I hope the original poster and the audience can benefit from this discussion. Honestly I don't understand what you are trying to clarify.



Edison Ortiz Sat, 10/06/2007 - 09:21

I wasn't contradicting your post. I started typing my reply, walked away for few minutes, came back and finished my sentence then hit post. That's when I noticed you've replied.

I agree no-so-stubby totally-stubby area will provide the desire result but without knowing the whole network topology, I'm hesitant to suggest one way of the other. That's the reason I asked for a diagram and also if he wants to see inter-area routes in addition of the intra-area routes.


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