Joe, This is actually documented at the link you quoted below: "For EBGP only, prefer the current active route when a route is received from different neighboring ASs, by default. To disable this default behavior, specify the external-router-id option at the [edit protocols bgp path-selection] hierarchy level."
--Stacy On Apr 1, 2010, at 4:53 PM, Joe Metzger wrote: > Does anybody have a reference to the real best path > selection process actually used by an M7i running 9.3 > that documents all of the tie-breaking criteria, and > when it might decide to just blow off recomputing a new > best route if the important attributes didn't change? > > I was poking around today on a router that is excepting > 2 identical iBGP feeds of routes to black hole. Approximately 70% > of the routes from 1 server were marked as best and 30% > from the other. > > The published selection algorithm docs only include deterministic > criteria, and so I would have expected deterministic results and > that the routes from the black-hole server with the lowest router > ID would be preferred 100% of the time. > > http://www.juniper.net/techpubs/en_US/junos/information-products/topic-collections/nog-baseline/topic-20357.html > > The underlying system feeding routes to the 2 black hole > servers guarantees that both servers are sending identical > lists of prefixes, with identical local-pref, as-path, > origin code, med value, source protocol, etc. The import > policy explicitly sets the next-hop to discard for all > routes from both servers so IGP distance shouldn't be a factor. > > The only differences between the routes announced from each > black hole server visible in show route extensive are router > ID, Task, and the time that the route was announced. It appears > that it is showing the oldest route as the 'best' one. > > This isn't causing me any trouble, but it looks wrong, and making > routing decisions based on age has bit me in the past. :-( > > > > Joe Metzger > [email protected] > > > > _______________________________________________ > juniper-nsp mailing list [email protected] > https://puck.nether.net/mailman/listinfo/juniper-nsp _______________________________________________ juniper-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/juniper-nsp
