In message <[EMAIL PROTECTED]> "Yue Wang" writes: > > > > Assuming the 1-hop route is lower cost, this shouldn't be necessary. > > Look at section 3.8.1 in RFC 2740. Every router advertising anycast > > addresses simply advertises the closest anycast address. How this is > > accomplished is an implementation specific matter and depends how > > the anycast addresses are discovered - is that what you're > > trying to accomplish with your route lists? > > > > No, my point is: the 2-hop route will update the 1-hop route because > the current OSPF thinks it newer, if we simply treat anycast as > unicast. Note that an anycast address can be on multiple locations. > And I use the anycast route list to maintain this information.
I assume that you are talking about inter-area or ASE routes since OSPF is LS and exchages topology, not routes within an AS. It could also be stubs within an AS. (Excuse the OSPFv2 centric terminology but I find stub, inter-area, and ASE simpler than vertex attached LSAs or whatever). For a stub route, if a the router (vertex) is adjacent to some non-trivial topology (served by RIP2 <gag> for example) the router advertises the *best* route it has to any given prefix, not the most recent. If a 2 hop stub is advertised by a router then it is because it is now the best route (for example, the 1 hop route may have gone away due to a link failure that was learned by RIP2). For an inter-area route the same applies. If a two hop (or higher cost we should say) route is advertised by an ABR then it is because that is now the best route, not because it is the most recently used. Save applies to ASE. If two routers advertise the same stub (same prefix), then in OSPFv3 terms there is one LSA for each of the two vertex in the topology. >From any router in the topology the closest one is the one who's sum of cost to reach the vertex plus stub cost is lowest. This is not uncommon. The same applies to the same inter-area or ASE advertised by two or more ABR. This happens all the time (to the extent ASE is used at all) since multiple ABR are used for any given area for redundancy. Each ABR advertises the *best* not the most recent route. Within the area there is one LSA per ABR (vertex) advertising this prefix. You may be confusing OSPF with some other routing protocol. Your characterizatin of how OSPF works is incorrect. If you start out with an incorrect fundamental premise, you are likely to reach a false conclusion. That seems to be the case here. You've made an incorrect assumption about how OSPF works and concluded that ODPF needed to be changed to support what you want to do. Curtis _______________________________________________ OSPF mailing list [email protected] https://www1.ietf.org/mailman/listinfo/ospf
