QID:NA354

[kwmir]

the "correct answer" seems to be incorrect.  I cannot find any supporting information for the claim "this default route will be excluded because this route is pointing to RT2 itself."  Can anyone explain how this occurs?

[gtrunner]

the route isnt learned because  if it did it would make a routing loop. ospf is a link state routing protocol so each router comes up with its routing table based on its own SFP algorithm. The RT1 router sent the LSA to the RT2 router (with the route 0.0.0.0 0.0.0.0 serial 0/0 *172.16.100.1*) this IP is all ready known by the the RT2 router so it doesn't add it to the routing table.   
 

[zuo123]

yes,I cannot find any supporting information for the claim "this default route will be excluded because this route is pointing to RT2 itself."

[ggw]

I agree. I have simulated this configuration on Packet Tracer and everything works well except for the problem with the routing loop. Neighbors are established, the default route is forwarded to the adjacent router (labeled as (O E2*), full routing tables are learned and all works well until one tries to send a packet which is not in the routing table. The answer H2P gives is definitely incorrect. A good question.