[c-nsp] OSPF LSA Type 3 / 5 question ...

[Bryan Holloway]

Hello everyone,

Wondering if anyone has an idea on how to resolve a summarization 
conundrum I'm having.

Imagine an ABR bordering areas 0 and 1 which is summarizing 10.0.0.0/8 
to the backbone.

Downstream is a router running OSPF with the ABR. On that router is a 
static route to yet another device that does not support OSPF. Let's say 
that static route is 10.100.0.0/24.

Since it's a static, I go ahead and "redistribute" it into OSPF.

This generates a Type 5 External LSA which then propagates to the rest 
of the backbone and other areas.

The problem is that since I'm already summarizing 10.0.0.0/8, I don't 
want that External LSA to show up everywhere. I really only care that it 
appears in the ABR routing table so that packets arriving at the ABR 
know how to get to the downstream router. The rest of the world is 
already getting the summary.

Has anyone run into this and/or have an idea how to suppress the 
external LSA beyond the original ABR? I could filter at the other area 0 
routers, but this obviously doesn't scale well.

In other words, is there a clever way for the ABR to detect that the 
Type 5 LSA is within the range it's already summarizing (Type 3) and 
suppress its upstream announcement?

Thank you!
			- bryan