Future stub area without area 0

Answered Question
Oct 30th, 2007

Hi,

the next week I am configuring a network "A" that will use OSPF as routing protocol with area number different than 0.

This network is also connected to Internet.

This network will be connected the next year to another network "B" that will ve configured as OSPF area 0 and it will become a stub area.

Could the network "A" work correctly (for example for Internet connection) during the transition period without connection to an OSPF area 0?

Thanks in advance

Antonio

I have this problem too.
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Correct Answer by Kevin Dorrell about 9 years 2 months ago

Yes it will. A non-zero area will work OK. But the one thing it will not do is share routes with anything that isn't area 0. So you should be OK since you only have the one area.

Be aware that when you convert it into a stub, you will have to convert all the routers to stub at the same time. A router that thinks a certain area is a stub will not talk to a router that thinks the same area is not a stub.

Actually, if it is going to have the Internet connection, it might have to be an NSSA. I think you should be able to get away with making it an NSSA from the very start - that would save the migration headache.

And if you want to make it a totally stubby NSSA (totally-stubby-not-so-stubby-area ha ha!), then you will only need to do a no-summary on the area border routers.

Would anyone else care to comment on that?

Kevin Dorrell

Luxembourg

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Correct Answer
Kevin Dorrell Tue, 10/30/2007 - 10:00

Yes it will. A non-zero area will work OK. But the one thing it will not do is share routes with anything that isn't area 0. So you should be OK since you only have the one area.

Be aware that when you convert it into a stub, you will have to convert all the routers to stub at the same time. A router that thinks a certain area is a stub will not talk to a router that thinks the same area is not a stub.

Actually, if it is going to have the Internet connection, it might have to be an NSSA. I think you should be able to get away with making it an NSSA from the very start - that would save the migration headache.

And if you want to make it a totally stubby NSSA (totally-stubby-not-so-stubby-area ha ha!), then you will only need to do a no-summary on the area border routers.

Would anyone else care to comment on that?

Kevin Dorrell

Luxembourg

Edison Ortiz Tue, 10/30/2007 - 14:30

Kevin,

Fully agree with your post. However, you can get away with stub while having the internet connection.

You don't need to redistribute to generate a default route so downstream routers know how to get to the gateway of last resort. The gateway of last resort would have NAT and another routing protocol for its internet connection.

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