No, I think you understand it perfectly. The goal is to have 'stateful knowledge' of my own eBGP routes, using the simplest most resilient and cross-platform compatible method.
What would be the caveats of the neigbor x.x.x.x allowas-in? It seems too easy, there HAS to be a catch! :) Do I need to change my inbound filters? Right now I am not filtering inbound routes from the directly connected Tier1's. -- Randy ---------- Original Message ----------- From: <[email protected]> To: <[email protected]>, <[email protected]> Sent: Wed, 2 Sep 2009 21:42:22 -0500 Subject: RE: [c-nsp] BGP multihop between two sites > Ah I think I see. Assuming you have no default route learned via eBGP then > (given 3 full routing tables, that's probably a fair assumption), the > question becomes whether you can intelligently maintain a floating static > default based on reachability to the next-hop IP, or if it's better to > implement some kind of BGP peering between the two sites. > > One possibility might be to consider a conditional static default route - use > "ip sla" to test next hop reachability of a provider's router, then use the > track command to monitor and apply to a floating default route (and of > course, you can do this for more than one provider and provide a > predetermined sequence of alternate default routes) > > I am not personally a fan of iBGP "raw" over a public network (and that's > what it would be since the ASNs are the same on both ends), as most of the > protection features in IOS are focused on eBGP. GRE tunnel works, though > there may be caveats depending on MTU/fragmentation issues and hardware > switching support. Maintaining those BGP peers of course assumes that the > remote IP in each case is known in one of the active eBGP sessions at all > time. Probably a reasonable assumption if you're using provider-owned IPs to > peer; maybe less so if you're using IPs that fall within your own larger > block. > > I may be misunderstanding something about your particular topology, so my > apologies if so. > > John. > > ----------------------------------------------------------------------- From: Randy McAnally [[email protected]] > Sent: Wednesday, September 02, 2009 21:10 > To: Herbert, John; [email protected] > Subject: RE: [c-nsp] BGP multihop between two sites > > > > I'm not quite clear on the floating default? What is it floating "over"? If > > you are receiving a default in BGP, > > then are you / can you receive it from multiple providers for resiliency? > > And if so, under what circumstances > > is the floating static ever active in your routing tables? > > It's a high distance static default route in place, to keep packets flowing > in case of an eBGP malfunction. In this case, it was routing packets between > locations because the prefixes were not in the routing tables. This was not > discovered until the provider the default pointed went down. > > -- > Randy > > > ------- End of Original Message ------- _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
