Survey on IBGP persistent route oscillation problem

Thu Mar 21 17:42:19 UTC 2002

danny at tcb.net disait :

> > We have a similar situation (RR + always-compare-MED off), and the BGP table
> > version keeps changing at 1K/min (http://performance.cn.net:2003/). I
> > suspect some
> > route meet the criteria of IDR-oscillation draft. But in real world, it's
> > very hard to pick
> >  up the pattern depicted in the draft from a huge log of debug bgp output.
> 
> It's actually quite trivial to identify.  Have a look at:
> 
> http://www.cisco.com/warp/public/770/fn12942.html

As Yu said, it is not so easy.
Most of the output in "show ip route bgp | include , 00:00" command match
flapping updates that are getting "dampening candidates" !!

Beside, you have to run the command on a router that might hit the
problem .... it depends a lot on your peering locations and partners.
If you run Cisco commands on wrong router, you would not see any
problem and may get in wrong conclusion !!

> > 2. From my experience, most flapping seems to be oscillation route 
> > which escaped the eBGP damping protection. And for this, we need 
> > adjust damping parameters from RIPE 220 to make up.
> 
> Nope.  Dampening doesn't resolve this because it occurs
> intrA-domain.

Does not fix, but it would lower updates thus help to identify
update loops.

Vincent.