OSPF and default routes

jdevoll · ‎03-21-2007

Please refer to the attached diagram.

S2-VPN has a static default route to ISP1. S2-VPN and S2-MPLS are both configured for OSPF area 0, they have a complete neighbor relationship and are exchanging routes. I added the 'default-information originate' statement into S2-VPN, and S2-MPLS wasn't getting the default route. I added 'default-information originate always' to S2-VPN, and S2-MPLS received the default route. I am looking for a clarification on when the 'always' qualifier is necessary. It is my understanding that always is only necessary when you want to advertise a default route even when a default route doesn't exist in a routers routing table.

S1-VPN has a static route configured so I was a bit surprised to need the 'always' qualifier. Can anybody shed some light on this for me?

Thank you!

sundar.palaniappan · ‎03-21-2007

Hi

Your understanding is correct. The 'always' keyword would only be required when no default route exists in the routing table but the router is asked to originate the default route anyways.

In your posting you stated 'S1-VPN has a static route configured' and I assume you meant 'S2-VPN' because I don't see S1-VPN anywhere. Can you clarify that?

Can you post the output of 'show ip route 0.0.0.0 0.0.0.0' from S2-VPN.

HTH

Sundar

jdevoll · ‎03-22-2007

Ah yes, that was a typo. It should state that "S2-VPN has a static route."

The static route is

ip route 0.0.0.0 0.0.0.0 10.255.255.17.

I suspect that this is a bug but I needed a sanity check to make sure I wasn't misunderstanding any subtle nuances related to the command.

sundar.palaniappan · ‎03-22-2007

Agree. What you are seeing isn't normal.

The good thing is it's atleast working with the always keyword :-)