Hi, Am 14.08.2018 um 11:01 schrieb adamv0...@netconsultings.com: >> Thomas Schmid >> Sent: Friday, August 10, 2018 10:35 AM >> >> it turns out you run into funny situations with that 'update wait-install' >> command enabled: >> >> RTA: 'update wait-install' configured. Learns route a.b.c.0/24 from direct >> peer >> ISPA. >> >> RTB: learns a.b.c.0/24 from eBGP peer ISPB with longer AS-path. >> >> RTA, RTB in BGP full mesh. >> >> If I prepend the route for a.b.c.0/24 on RTA, the local BGP table is updated, >> but the announcement with the longer as-path *never* makes it to RTB, >> probably because the CEF entry locally is not updated and does not change. >> So RTA is holding back the BGP announcement of the longer route to his >> neighbors. >> >> So RTB never sees the longer as-path for the prefix and therefore *never* >> announces the shorter route via back to RTA. Therefore the routing never >> changes in the network. >> >> In addition: 5.3.3 has bug CSCuv02045 "Mutex in ipv4_rib/ipv6_rib when >> update-wait-install is enabled" ... >> > Sorry for the late response, > > Well you've got to be careful here, > You haven’t stated that, during initial conditions, A believed that path via > ISPA has been selected as the overall best path indeed. > Cause if A believed that route via B from ISPB is the overall best path ,then > A would not advertise its own route to B (unless A is configured with > "advertise best-external" which I recommend in order to speed up convergence > -please note though it increases FIB usage). > > If, during initial conditions, A did select path via ISPA as the overall > best path then I agree it’s a bug and should be reported. > (would be interesting to see from debug why the route is not advertised to B) > Also I believe that update-wait-install routine should not be used in this > scenario (should be used only when a path is changed to best path). >
according to TAC, the behavior observed is intended behavior. No change in the CEF table -> no BGP update announcement. This leads to a classical deadlock situation. 'advertise best-external' might indeed help, but as you said, FIB usage goes up a lot when you do this for e.g. upstream connections. > Seems like CSCuv02045 has been fixed only very recently ~6.2.2+ > Isn't there a SMU available for older releases? > no SMU for 5.3.3 Cheers, Thomas
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