Bruno, To my mind, the purpose of graceful shutdown is to tease out the hidden paths before sending the withdraw. In your cases, the alternative paths are not hidden. They are already available. If they are available to the gshut initiating router, then they are available to the other routers. Therefore a withdraw is ok.
Now, consider a not uncommon case: The gshut initiating router has 2 advertiseable paths. Another router has an inferior path. When the gshut is initiated for one path, the inferior path from the other router will be chosen by the network. When gshut is removed, the network will churn a second time when it chooses the second path. I think it's better for the gshut initiating router to just advertise its next best path instead of gshut. Thanks, Jakob. > -----Original Message----- > From: GROW [mailto:[email protected]] On Behalf Of > [email protected] > Sent: Tuesday, June 27, 2017 6:15 AM > I'm not following you, so I'll provide an example of "not allowed to be > advertised on IBGP" > Topology: the g-shut initiator has an IBGP session with another ASBR (e.g. > ASBR1 in the same POP). This ASBR knows > an alternate path and advertise it over IBGP. (e.g. best external, or > EBGP>IBGP) > g-shut convergence: If the g-shut initiator applies the low local_pref, it > will switch to this alternate path. As it > can't advertise over IBGP a path learned over IBGP, it will send a withdraw > to both its Route Reflector and its own > IBGP peer. > Discussion: May be we could assume that its Route Reflector and IBGP peers > also have the pre-knowledge of this > alternate path (from ASBR1) in which case this is not a big deal. But in > theory, it's just safer to never send a > withdraw. _______________________________________________ GROW mailing list [email protected] https://www.ietf.org/mailman/listinfo/grow
