> One of the issues we found (Philip Smith and I) "back then" was indeed > router bugs. The combination of "export policy is changed" with "an > update is queued for this neighbour right then" led to control-plane > confusion and missing withdraws. This was fixed.
cool > 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. 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). randy
