[c-nsp] Sanity check OSPF/BGP

[tim at pelican.org]

On Thursday, 8 October, 2020 17:08, "Drew Weaver" <drew.weaver at thenap.com> said:

> Previously, when we had this issue it was determined that it was because there was
> still a route to the BGP neighbor in the routing table (because the neighbor IP
> was part of our IP announcements and it would wait until the hold time to expire)
> but we got around that particular issue by using RFC1918 IPs for the neighbors and
> BGP Next hop address tracking took care of the rest (made it much faster, like 1-2
> seconds) but it seems like in our current architecture with the new core
> it’s operating differently.
> 
> It’s almost like the new core routers are continuing to be seen as a path to
> this neighbor by the old core routers and vice versa even though OSPF went down on
> both of them at the same exact time.
> 
> It’s a mystery for sure.

Back to basics - what does "show ip route <remote-loopback>" give you during that two-minute window?

Is there a default route somewhere in the network that could be flagging that remote loopback as still reachable until the BGP timers expire?

Regards,
Tim.