[c-nsp] NSSA default route forwarding address

[Justin M. Streiner]

On Wed, 6 Dec 2006, Dimitrios Kalogeras wrote:

>> This is correct.  If an OSPF speaking router does not have a loopback
>> address, it will use the highest-numbered IP address that it has on one of
>> its interfaces as its router ID.  If the router in question has many
>> interfaces or its overall topology changes often, you could introduce some
>> IGP instability if a new interface is added with a higher IP address than
>> the existing router ID.  This would cause your OSPF adjacencies to drop
>> since hello packets would be sent out with a router ID different than the
>> ones that originally established the adjacency.  It would also likely
>> cause your OSPF process to reset.
>>
> My router has a loopback interface in area 0 and a router-id set
> specifically set for that reason. However the default route generation
> was for the nssa area and not for the backbone area. Does this mean I
> have to create another one for the nssa area ?

That's what I get for reading and responding too quickly, I guess :)

If I'm understanding your situation more clearly now, then this might 
work.

Try changing the area type from an NSSA to a Totally Stubby NSSA, which 
you can do by changing all instances of "area XXX nssa" to "area XXX nssa 
no-summary".  You should see an LSA in the link-state database for that 
area, for 0.0.0.0/0, out to area 0.

I think the Totally Stubby NSSA was a Cisco-ism from several 
years ago, created to address some of the shortcomings of stubs, Totally 
Stubby Areas, and Not-So-Stubby Areas, namely allowing the importation of 
a type-7 external LSA for default.

Hopefully this answer is a little closer to what you're looking for :)

jms