[c-nsp] All OSPF adj/neigh flapping every 30-35 minutes

[Church, Chuck]

Are there any spanning tree topology changes occurring between the 3
devices?  That could explain the flaps, as hellos could be lost for a
shot period of time.


Chuck Church
Network Engineer
CCIE #8776, MCNE, MCSE
Multimax, Inc.
Enterprise Network Engineering
Home Office - 864-335-9473 
Cell - 864-266-3978
cchurch at multimax.com

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of
christopher.a.kane at jpmchase.com
Sent: Friday, September 29, 2006 11:12 AM
To: John Smith
Cc: cisco-nsp-bounces at puck.nether.net; cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] All OSPF adj/neigh flapping every 30-35 minutes

>Greetings, 
> 
>  I have a question about OSPF adjacency flapping. I have 2 OSPF 
neighbors on a router; via 2 Gigabit Ethernet links. >Both of the 
neighbors flap every 30-35 minutes. The logs on the routers do not show 
any other events; no physical >layer issues. Is there a command that
will 
tell me what's causing these neighbors to go up/down?
> 
>  --
>  Thanks!
>  John

Yes, there are some debugs that may help but it depends on the actual 
cause. Are the neighbor adjacencies actually breaking? Do you have 
log-adjacency-changes enabled under OSPF and see the neighbor DOWN, 
LOADING, FULL type messages in the log?

I can't initially think of anything that would cause a time-predicatable

adjacency break. There is a refresh of LSAs every 30 minutes (any
network 
locally originated must be refreshed every 30 minutes). But that
wouldn't 
cause a neighbor flap. Are you running IKE/IPSec or anything else time 
based that could be prohibiting OSPF Hello packets through? Are the 
routers directly connected on those gig links? Or do they run through a 
pair of L2 switches in between that may be having some sort of problem?

-chris


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