[c-nsp] Sanity check OSPF/BGP

[Drew Weaver]

Those are both good questions. I didn't catch it when it occurred but I will remove traffic from the PE router and then simulate the failure.

Thanks,
-Drew


-----Original Message-----
From: cisco-nsp <cisco-nsp-bounces at puck.nether.net> On Behalf Of tim at pelican.org
Sent: Thursday, October 8, 2020 12:27 PM
To: 'cisco-nsp at puck.nether.net' <cisco-nsp at puck.nether.net>
Subject: Re: [c-nsp] Sanity check OSPF/BGP

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.


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