[c-nsp] Different Areas OSPF Paths

[Shakeel Ahmad]

Hello Guys,

I am in a little trouble here, 2 questions ! please give away your comments,
picture might help you to understand the scenario:

Scenario:

In a multisite network enviornment, SITE-A is having multi-service providers
and making GRE tunnels with Site-B & Site-C.

Site-A is running backbone Area 0, while all boundry routers are acting as
ABR for Area-4 & Area-3 via GRE Tunnels

Picture: http://70.84.169.162/~shakeel/OSPF.jpg


Problem:

Route-Site-A-2 is the lowest cost to reach Site-B , On Core router at Site-A
you'll see Router-Site-A-2 and Site-B as a selected path....but when you go
to any ABR... you'll see its own Tunnel as the best exit path via OSPF,
although other ABR's are recieving shortest path via OSPF neighbours.

In OSPF RFC i read:

> the order of preference for OSPF routes is:

> intra-area routes, O
> interarea routes, O IA
> external routes type 1, O E1
> external routes type 2, O E2



so how do this issue justifies with another opinion by a cisco's expert that


"As being in a different area, OSPF will opt for the nearest exit - It pays
no attention to the metric on the link...."


Another question is: Area-3 doesn't wantes to recieve routes from Area-4 and
vice versa but connection to Area 0, is distributing the routes/flooding to
both these areas.

I have tried making both Area 3 & 4 a stub but it's not helping...next thing
i tried was to drop the routes coming active by filter-lists in OSPF but
obviously it's not stopping the OSPF database packets...what can be the
possible solution..


thanks in advance...

Shakeel