[c-nsp] Dual-homing scenario

[Niels Bakker]

* vincent at dekeyzer.net (Vincent De Keyzer) [Thu 22 Feb 2007, 13:40 CET]:
>let a dual-home BGP network. ISP1 comes in with a T3 and sends a full BGP 
>table; ISP2 comes with a FE and a default-route (for memory reasons).
[..]
>One way I see to achieve this would be to local-pref based on AS path: 
>if the route comes from ISP1's AS, or from an AS directly connected to 
>ISP1, local-pref it with 130; else local-pref it with 100 (and 
>local-pref the default route from ISP2 with 120).
>
>Is this a good way to do it?

It's not.  Localpref won't override longest-match route selection, only
AS_path length check.

You have three options:

0) Buy a real router to multihome with instead of something with not
   enough memory (and probably also forwarding capacity)
1) Keep the current setup from ISP1 and ISP2, but filter ISP1's routes
   to default-only plus whatever routes you want from them
2) Get two full feeds but filter them aggressively to save memory and
   rely on default routes for destinations where you filtered the
   more-specific.

HTH


	-- Niels.

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