[routing-wg] New on RIPE Labs: BGP Zombies
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Gert Doering
gert at space.net
Wed Apr 24 17:15:24 CEST 2019
Hi, On Wed, Apr 24, 2019 at 08:06:18AM -0700, Randy Bush wrote: > > My conclusion then was that something along the following line happens > > > > - router R1 remembers where an UPDATE was sent to > > - export policy on R1 is changed, changing whether or not a given > > peer would receive an UPDATE for a given prefix > > - R1 receives withdraw from his best (and only) path, prefix is gone > > - R1 sends withdraw to "all peers it remembers" > > - and something goes wrong if that list of peers is not reflecting the > > real set of peers, possibly due to "BGP internal state not fully in > > sync between 'export policy is changed' and 'withdraw comes in'", so > > R1 is no longer aware that one of his neighbours received the prefix > > originally. > > believable conjecture. could and should be tested in lab. Indeed. > but does not explain the cases where we see stuck routes on devices > which have no config changes for a loooong time (if you believe rancid). Well, in the scenario above, R1 would have the config change, but *on R1* the route would be gone. A downstream router R2 would have seen the initial UPDATE, but never received a withdraw - so R2 would claim "I have it, and I have it from R1!" while R1 would claim "no such prefix". So, no contradiction. Gert Doering -- NetMaster -- have you enabled IPv6 on something today...? SpaceNet AG Vorstand: Sebastian v. Bomhard, Michael Emmer Joseph-Dollinger-Bogen 14 Aufsichtsratsvors.: A. Grundner-Culemann D-80807 Muenchen HRB: 136055 (AG Muenchen) Tel: +49 (0)89/32356-444 USt-IdNr.: DE813185279 -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 833 bytes Desc: not available URL: <https://lists.ripe.net/ripe/mail/archives/routing-wg/attachments/20190424/c1b4342d/attachment.sig>
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