mailing list archives
Re: weird BGP cisco-ism? [problem resolved]
From: "Barry A. Dykes" <bdykes () genuity net>
Date: Fri, 11 Jul 1997 17:40:35 -0700
Why don't you just tag your exportable routes and let them through,
while blocking everything else? You could then build a route-map that
places that tag on all of your inbound BGP customers. This would allow
you to export everything that they send you (allowing them to send the
more specific as Dorian stated) and use a static tag for your aggregate
routes. Then all the more specific routes on your backbone would be
filtered, unless it originated from a BGP customer - who would need to
send the more specific advertisements to each of it's providers and
allow routing to work correctly. I know, that's what we do! If you
don't have the right tag, you don't get off! And I don't have to mess
with any filters after they are set up.
You can remove the specifics at the edges of your network either via community
based filtering or prefix based filtering. The former is much more flexible
and is the one I'd recommend.
I'd think prefix based filters would be more likely to be correct.
Since you have to explicitly list what you think you should be announcing
you protect against having routes you don't expect in your tables and
against having interactions that cause unexpected routes to get tagged as
-Chris (cgarner () sni net)
- Re: weird BGP cisco-ism? [problem resolved], (continued)