-----Original Message----- From: Jeff Wheeler [mailto:[email protected]] Sent: Thursday, January 03, 2013 6:49 PM To: Saikat Ray (sairay) Cc: [email protected]; [email protected] Subject: Re: [Idr] [GROW] I-D Action: draft-ietf-grow-ops-reqs-for-bgp-error-handling-06.txt
On Thu, Jan 3, 2013 at 9:37 PM, Saikat Ray (sairay) <[email protected]> wrote: > If a transit router in your AS treats-as-withdraw a prefix, other routers may > try to send traffic across it, but the router which has treated-as-withdraw > will either have no information for that route, or it will have made a > different bestpath choice. This could cause a loop or a blackhole. > > [SR] If the transit router treated the prefix as "withdrawn", then it will > remove the corresponding path. If there are no other paths for that net, then > the router would send withdraws for that prefix to its own peers. So no other > router would send traffic to it in the steady state. Perhaps you read "ASBR" where in fact I wrote "transit router?" The behavior you describe is wrong. [SR] Wrong in what sense? BGP code does not care whether it is a transit or an ASBR. What I described is exactly what the code will do. (i) a path for a prefix (a "net") is withdrawn. (ii) BGP deletes the path from that net. (iii) BGP reruns bestpath computation. (iv) If the bestpath changes, (a) if there is a new bestpath, then BGP readvertises the new bestpath to all its peers (b) if there is no bestpath (which would be the case when there is no path for the net), BGP will send withdraws to all its peers. -- Jeff S Wheeler <[email protected]> Sr Network Operator / Innovative Network Concepts _______________________________________________ GROW mailing list [email protected] https://www.ietf.org/mailman/listinfo/grow
