This is kind of a split-horizon/poison-reverse question, but here we go.
In a very simple network, lets say we have the following:
Let's say A learns the default route 0.0.0.0/0 from both B and C, and they both have the same exact metric, and those are the same links (both 1 gig for example).
Will A advertise to C the route it learned from B, and will A advertise to B what it learned from C if both routes in A's routing table are equal cost?
I spent some time in my lab, and when A was a 6500 with equal cost metrics, there was no updates from A to B / C. B/C did NOT have an entry in the topology table for 0.0.0.0/0 via A.
When I made my 4507 A, I DID see it update only ONE of the neigbhors.
Whichever came up first it did not update. So if B sends A the route, and then C sends A the route, A sent C a route about B, but it didn't send B anything. C did have a topology table entry for 0.0.0.0/0 via A (it was NOT a FS, however -- understandably so).
Now I don't know why I'm seeing different behavior, so that's why I'm here. I think if it's equal metric the switch should NOT send an update back.
Thanks for any / all feedback!