nanog mailing list archives

Re: Route Supression Problem


From: Iljitsch van Beijnum <iljitsch () muada com>
Date: Wed, 12 Mar 2003 20:02:24 +0100 (CET)


On Wed, 12 Mar 2003, Danny McPherson wrote:

Dampening is done on the eBGP router where the route enters the AS, and,
unless I'm mistaken, per route/path and not per prefix. So the flapping
that ISP A sees from ISP B is a completely seperate thing from the
flapping that ISP A sees from its customer's customer as far as the
dampening algorithm is concerned.

Nope.  It's per-prefix.

If that is the case then dampening is severely broken, because then a
router that receives a prefix over two paths will lose *both* if _one_
flaps.

In any case, it is done on the eBGP router receiving the prefix/route,
so unless the two ISPs in question peer using the same router as they
use to connect to Jack's AS, there still shouldn't be any flapping
multiplication. (Hm, unless that happened inside Jack's network...?)

Iljitsch


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