As well could put a GRE Tunnel or VLAN between the two ASR's and run iBGP between the two. You control the path between the two routers, so the tunnel can be over a jumbo frame capable path. I would still do a selective advertisement for the default, so that traffic doesn't need to traverse the both routers, but this would stop the blackholes for routes unlearned. Especially if it is the upstream that is having issues, instead of the direct connection.
David -- http://dcp.dcptech.com -----Original Message----- From: Adam Vitkovsky [mailto:[email protected]] Sent: Thursday, September 27, 2012 4:41 AM To: 'Tom Lanyon'; 'David Prall'; 'cisco-nsp' Subject: RE: [c-nsp] Change BGP default-originate to IGP? So if I understood it correctly you are concerned that the router will start to originate the default prior to receiving full BGP table from its upstream right? The simplest solution would be to place a static default route pointing to the upstream -so in case of the above happens the router wouldn't blackhole till it gets the full feed. Or you can base the condition of default advertisement on several prefixes from all around the place instead of just one -but trying to match e.g. 10 prefixes from 400k well... The problem with this though is that on IOS you can't AND the "match ip address" statements under the route-map only OR -applies to all the match statements of the same kind. So you could use static routes for the list of desired prefixes each with a high AD -redistribute them into bgp with specific community and match for the prefixes+community in "non-exist map". So once you'll get all the prefixes from BGP -only after all cease to exist in the bgp table with the specific community of yours -the router will start to advertise the default route. adam -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Tom Lanyon Sent: Thursday, September 27, 2012 4:58 AM To: David Prall; cisco-nsp Subject: Re: [c-nsp] Change BGP default-originate to IGP? Is there a specific order in which BGP updates are sent/exchanged/processed? The concern I have with tracking upstream routes is that the route tracked would need to be one of the last routes received (if not the last) to ensure that the router has full visibility. This seems quite non-deterministic and so potentially fraught with 'weirdness'. Thanks, Tom On 27/09/2012, at 12:19 PM, David Prall wrote: > Why not use selective advertisement of the default based on receiving > a specific route from your carrier or an upstream you know to be stable. > > http://www.cisco.com/en/US/docs/ios/12_3/iproute/command/reference/ip2 > _n1g.h > tml#wp1037042 > > David _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/ _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
