[c-nsp] BGP conditional advertisemet - NON-EXIST route map's access-list problem

[Yan Filyurin]

If you want ISP 2 to be used as a backup for ISP1 inboud traffic could you just advertise your routes to ISP2 with, say bigger AS path to the point where even ISP2 thinks it is best to go somewhere else than directly to you?  

As far as conditional advertisement goes. Mateusz is absolutely right and you just have to pick a route, which will go into your non-esist-map.  Also as you are advertising routes to ISP2, it may make sense to create a regular outgoing route map to make sure you are not advertising ISP1 routes to ISP2, so only your route matches.  That is where you can match on the AS path.  Then you can just have an access list or prefix list in your advertise map, which can decide whether to advertise it or not. 

You could also create a static route that would be conditional on some IP SLA condition and have your route generation or conditional advertisement based on that, but that would just be weird. :)

Yan



________________________________
From: Mateusz Blaszczyk <blahu77 at gmail.com>
To: Burak Dikici <bdikici at gmail.com>
Cc: cisco-nsp at puck.nether.net
Sent: Sunday, March 15, 2009 10:53:25 AM
Subject: Re: [c-nsp] BGP conditional advertisemet - NON-EXIST route map's access-list problem

Burak,

> ip as-path access-list 1 permit ^200 !!! (ISP-1 AS number) !!!
>
> access-list 65 permit any !!! (permit any packet from ISP-2) !!!
>
> route-map NON-EXIST permit 10 !!! (this matches any route from AS200) !!!
> match ip address 65
> match as-path 1

you can match only on ACL and prefix-list int the *-EXIST-MAPs.
Also you dont match packets rather prefixes.

So choose a ISP-1 prefix (some infrastructure IPs or so) and match in prefix-list/route-map.
Then if it is gone, start advertisiing to routes in ADVERTISE

Best Regards,

-mat

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pgp-key 0x1C655CAB