OSPF Duplicate Router-id - problem areas

Hello,
I have a quick question regarding OSPF Router-id uniqueness. I know that
router-id needs to be unique in OSPF. So I did some testing.

Looks like in the same area you'll run into problem.

I'm thinking that if you have virtual-links, then yeah that would give your
problems.

You can't have any ABR or ASBR with router-id that are duplicate, that is a
problem for sure.

In you have member routers in different areas with duplicate router-id,
you'll run into problems if one of the routers sharing the same router-id
is originating an external route (FLOOD_WAR).

But outside of that, everyone else would see the advertising router as ABR
and not the router with duplicate router-id so that should be ok.

Are there any other scenarios? Seems to me saying that the whole AS needs
to have unique router-id might be too general and there are few cases where
you won't need that. I'm not saying to start configure them duplicate, but
just exploring the concept further.

Thank you very much in advance for any input.

Tom Kacprzynski

Blogs and organic groups at http://www.ccie.net
Received on Wed Dec 21 2011 - 23:40:42 ART