On Thursday, May 10, 2012 04:06:26 AM Morgan McLean wrote: > Also, just to add to this, if I try to deny a route by > neighbor or next-hop, the entire route is denied > regardless of where it comes from. > > If I try to deny the export of a route from protocol > static on the announcing router, again it doesn't matter > to which neighbor, it denies the entire route. > > Am I just SOL? BGP is so much easier to work with....
Link state routing protocols don't generally like to be filtered, as a consistent, holistic view of the global network topology is the only way to avoid loops in your link state IGP network. Yes, there is some kind of filtering available in routing implementations for link state routing protocols, and as you can see, it behaves rather strangely and might not do everything you want, the way you want or expect. For some implementations, I've seen filtering on inbound to be more successful, while in others, it's been the reverse. At the heart of it, while it is possible to filter prefixes being announced/received, the filters don't really filter the entire IGP message, as what is exchanged among neighbors is LSA's (OSPF) and LSP's (IS-IS), and not routes as in the case of BGP. I have been in your exact situation before where we've had to originate a default route to various Access switches in Metro-E rings, and IS-IS seemed like an obvious way to do it between the PE Aggregation routers and the Access switches directly. But while you could originate the default route to the Access network, it wasn't easy to prevent said route from being announced to other parts of the network where it "wasn't" needed (especially since we were a flat Level-2 IS- IS network). Unlike BGP, route exchanges among neighbors is not unicast in nature (yes, it can be in certain cases), so controlling which routes/LSA's/LSP's go where isn't easy. We ended up going with BGP, getting those default routes announced to all Access switches from the control-plane-only route reflectors in the network, and relying on MPLS to ensure proper forwarding of traffic (away from the route reflectors that were originating those default routes). Hope this helps. Mark. _______________________________________________ juniper-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/juniper-nsp
