OSPF default route multiple processes

Hi all,

I have a situation within our data center where I have two OSPF processes
(each with only one area) and a single point of contact (border router)
between the two. I have OSPF process 51, area 51; and I have OSPF process 1
area 0.

Area 51 has a single Internet connection and the point where I do a
default-information originate (type 2; default metric)
Area 0 has two Internet connections and both do a default-information
originate (type 1; different metrics)
On the border router, there is mutual redistribution of all routes except
the default route which is filtered out in both directions (so each area
has it's own Internet exit)
The border router MUST take the default route from Area 51 always.

Well, I got this whole setup working stable for months now until last
Tuesday. And there's a default router on the border router from area 0,
while the Area 51 has the better metric (1) versus metric 10 and 20 from
Area 0.

QUESTIONS:

1. What is the order of operation within OSPF to select default routes from
different processes?

2. How do I ensure the border router ALWAYS takes the default route from
Area 51 (although it has multiple default routes from Area 0 in it's
database)? Since OSPF metric-type 1 has preference over metric-type 2, do I
change the metric-type in Area 51 to type 2 and ensure it's always lower
than from Area 0?

Looking forward hearing from you.

If you need more info, please let me know.

(Brian, I couldn't find any blogs on INE about OSPF multiple processes. Is
this an idea for a future blog post maybe?)

Cheers,
Marc

Blogs and organic groups at http://www.ccie.net
Received on Fri Jul 26 2013 - 18:50:14 ART