OSPF Default route selection when ECMP is disabled

Reply
Highlighted
L1 Bithead

OSPF Default route selection when ECMP is disabled

ISP1-----PA:1---------PA:2--------PA:3-------ISP2

I have a setup as above

All PA's are in single area 0.0.0.0 and links are type broadcast.
I am advertising a default route each from PA:1 and PA:3 to PA:2 with ext2.
When I enable ecmp on PA:2, I am able to see both default routes in RIB and FIB of PA:2.
When I disable ecmp,i am able to see only one default route either from PA:1 or PA:3 at a time.
My question is: with ecmp disabled, on what parameters PA:2 is calculating the cost and keeping a single default route in RIB and FIB?

Like what you see?

Show your appreciation!

Click Like if a post is helpful to you or if you just want to show your support.

Click Accept as Solution to acknowledge that the answer to your question has been provided.

The button appears next to the replies on topics you’ve started. The member who gave the solution and all future visitors to this topic will appreciate it!

These simple actions take just seconds of your time, but go a long way in showing appreciation for community members and the Live Community as a whole!

The Live Community thanks you for your participation!