Thanks Robert & Gert. I will go back to carrier as I have checked both changing 
attributes and my route to peer.

I have tested this in GNS3 with different IOS as well, and everything i stable.

Brad

________________________________
From: Robert Raszuk <[email protected]>
Sent: Saturday, 18 April 2020 8:26 PM
To: Bradley Ordner <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: [c-nsp] Default Route recalculated every 60 seconds.

Hi Bradley,

>From my cisco days I recall that you should not be seeing RIB being updated 
>over and over with the same route even if BGP keeps sending you implicit 
>withdraws in the form of new BGP UPDATEs. Of course I will not tell you if the 
>above is still identical today on all XE, NX & XR :)

However the above only works if your next hop is stable. If you are recursing 
your routes over BGP (double recursion) then yes you will see this churn going 
on into RIB.

But there is simple fix/test - just set a static route matching next hop of 
received BGP prefixes towards your eBGP peer with interface and IP address and 
see if it helps.

Cheers,
R.



On Sat, Apr 18, 2020 at 8:10 AM Bradley Ordner 
<[email protected]<mailto:[email protected]>> wrote:
I am about to leave an Enterprise environment due to Pre Covid-19 redundancy 
and I just need to find the root cause of this issue before I leave.

We recently built a Layer 2 Circuit over a Providers SDN Backbone so we could 
get a 2Gb Internet link. We peered with this neighbor and filtered a partial 
table, so we get about 30000 routes. For some reason, every 30 seconds the 
default route uptime resets to 00:00 in the routing table. I spoke with 
Carrier, they made a few changes and one was the BGP advertisement timer. It is 
now set to 60 seconds and now the default route resets every 60 seconds.

The carrier, keeps blaming my side so I opened a Cisco TAC case and they 
haven't got around to looking at it yet, probably because it really sounds like 
it is the carrier side. I took some packet captures and indeed every 60 seconds 
an update with the default is sent. Our router constantly accepts this, 
recalculates and enters it into the routing table.

I can't seem to figure out if this is some type of bug or not. The router has 
been rebooted and is due for IOS upgrade shortly, but wanted to see if anyone 
has seen this or point me in the right direction.

Thanks

Brad


_______________________________________________
cisco-nsp mailing list  
[email protected]<mailto:[email protected]>
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/
_______________________________________________
cisco-nsp mailing list  [email protected]
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

Reply via email to