OSPF default route in nssa-external as well as inter-area database

[Kashish_Patel]

I have a scenario where there are 4 routers in an nssa area.

Router 1 has three GRE tunnels to other three routers, these tunnels run ospf with different ospf costs.

R1 ----- R2

R1 ----- R3

R1 ----- R4

R1 has all interfaces in nssa area...R2,R3,R4 are generating default route using "default information originate"... I am seeing the default route generated by R2,R3,R4 in nssa-external database on R1....I also see default route generated by R2 and R3 in inter-area database on R1...And because of different costs, R1 is preferring default route coming via R2.....In reality, I expect the default route in just nssa-external database and not in inter-area database and so based on lower cost of R1---R4 tunnel, I expect R1 to prefer default route through R4...Why am I seeing default route landing up in inter-area database also?

Thanks.

[Harold Ritter]

Hi Kashish,

It probably has to do with the configuration of r2 and r3. Could you please provide the configs.

Regards

[Kashish_Patel]

Thanks for your reply, Harold. I sent you configs of all 4 routers in offline message...Let me know if you need anything else.

Regards.

[Harold Ritter · Accepted solution]

Hi Kashish,

The presence of the default route as an LSA type 3 is a direct consequence of the no-summary keyword on the "area x nssa" statement. The fact that you also see the default route as a LSA type 7 is normal behavior.

Please refer to the following document confirming that behavior:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a74.shtml#nssas

Hope this helps

[Kashish_Patel]

Thank you so much!