Dave Katz <[email protected]> wrote on 06/08/2009 20:24:25: Hi Dave :)
> > If there is no back link, there is no link, and SPF moves on. If the > network is partitioned, somebody should fix it. Yes, this problem exist for a short while, until the remote route has updated it's LSA. > > Ignoring the bidirectional test rule can lead to loops and black > holes, particularly if other implementations are following the rules. hmm, can you be more specfic? Consider this example: R1 R2 R3 | | | ------- N1 Destination is R3 and R2 is the calculation router. R2 cannot find a backlink so it falls back to the intervening router case and uses the nexthops from the "parent", hoping that one of them will redirect IP frames to R3. Jocke > > --Dave > > On Aug 6, 2009, at 8:02 AM, Joakim Tjernlund wrote: > > > "Joel M. Halpern" <[email protected]> wrote on 06/08/2009 15:38:47: > >> > >> I am not sure what you are asking. A link advertised in OSPF may > >> only > >> be used if it is advertised in both directions. > > > > Exactly, so you may encounter the scenario below when links are going > > down/up until all routers has recalculated everything. > > > >> Therefore, it appears taht the case you are describing can not occur. > > > > It can, so when it does you can either just give up or try > > to do the best you can until you find a back link. > > > > Jocke > > PS. > > Please keep the ospf list on the CC: line. > > > >> > >> Yours, > >> Joel > >> > >> Joakim Tjernlund wrote: > >>> In "16.1.1. The next hop calculation" one have: > >>> In the second case, the parent vertex is a network that > >>> directly connects the calculating router to the > >>> destination > >>> router. The list of next hops is then determined by > >>> examining the destination's router-LSA. For each link in > >>> the router-LSA that points back to the parent network, > >>> the > >>> link's Link Data field provides the IP address of a > >>> next hop > >>> router. The outgoing interface to use can then be > >>> derived > >>> from the next hop IP address (or it can be inherited from > >>> the parent network). > >>> > >>> Suppose that one cannot find any links that points back, is it a > >>> good > >>> idea to treat this case as a intervening router: > >>> > >>> If there is at least one intervening router in the > >>> current > >>> shortest path between the destination and the root, the > >>> destination simply inherits the set of next hops from the > >>> parent. > >>> That is, just inherit the next hops from its parents? > >>> > >>> Jocke > >>> > >>> _______________________________________________ > >>> OSPF mailing list > >>> [email protected] > >>> https://www.ietf.org/mailman/listinfo/ospf > >>> > >> > > > > _______________________________________________ > > OSPF mailing list > > [email protected] > > https://www.ietf.org/mailman/listinfo/ospf > > > > > _______________________________________________ OSPF mailing list [email protected] https://www.ietf.org/mailman/listinfo/ospf
