Hi,
Okay, I get the point. So, basically you want your ASBR to ignore the external routes redistributed by your ABR (which is also an ASBR but let's keep the distinction) while all other routers in the area should see them.
I believe that this is a use case for distribute lists on the ASBR - filter out the routes entering the routing table based on some additional criteria. Can you please check if the IOS on the ASBR supports the distribute-list route-map route-map-name in command in the OSPF process configuration? If it does then the solution should be relatively easy to implement. On the ABR, redistribute the routes into OSPF with a specific tag value, say, 123. The tag value can be specified in the redistribute command using the tag tag-value keyword. On the ASBR, use the following construct:
route-map FilterOSPF deny 10
match tag 123
match route-type nssa-external
!
route-map FilterOSPF permit 20
!
router ospf 1
distribute-list route-map FilterOSPF in
In OSPF, you cannot prevent LSA7 from being flooded throughout the NSSA area or from being processed at an arbitrary router. What you can do is only to prevent routes described by these LSA7 from entering the routing table, and this is what is accomplished by this.
Feel free to use the tag value and the name of the route-map as you see fit. Avoid the tag value 0 as that is the default tag value.
Best regards,
Peter
