Hi,
Please see diagram attached.
In an nssa no-summary area only a type-3 default route will be present the routing table of the routers. In the diagram IOU1 will receive Two ECMP type-3 default routes from IOU2 and IOU5.
In a failure scenario where the link between IOU3 to IOU5 and IOU3 to IOU2 goes down, traffic from IOU1 could be blackholed if ECMP decides to foward it to IOU3 having no valid links that are up and could forward outbound traffic.
Question, is there a way to do a conditional default route on the ABR so that it will not cause this blackhole scenario. Right now im not sure whether using NSSA in this type of design is recommended.
On the ABR, area x nssa no-summary will automatically advertise a Type-3 default route whether there is no present default route in the RIB.
Default-information-originate that has the capability of doing a route-map is advertised as a Type-5 so naturally the Type-3 will be proffered.
Any recommendations on this setup or suggestions for a better design?
regards,
Jon
