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List:       inet-access
Subject:    Re: BGP and default routes
From:       Lars Fenneberg <lf () elemental ! net>
Date:       2005-05-03 10:28:28
Message-ID: 20050503102828.GA9885 () gimli ! elemental ! net
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Josh,

Quoting Josh Higham (jhigham@pyrontechnologies.com):

> BGP routing table entry for 0.0.0.0/0, version 2
> Paths: (2 available, best #2, table Default-IP-Routing-Table)
>   Not advertised to any peer
>   19029, (received & used)
>     216.217.0.216 from 216.217.0.216 (216.217.0.216)
>       Origin IGP, localpref 100, valid, external
>   209, (received & used)
>     65.121.45.165 from 65.121.45.165 (205.171.3.236)
>       Origin IGP, localpref 100, valid, external, best
> 
> Network load is 871k in/1.2m out one connection
> Network load is 780k in/400k out the other

from the Cisco documentation:

	To be candidates for multipath, paths to the same destination need to have
	the following characteristics equal to the best path's characteristics:

	Weight
	Local-Preference
	AS-PATH length
	Origin
	MED

	One of the following:
	- Neighboring AS or sub-AS (before the eiBGP Multipath feature was added)
	- AS-PATH (after the eiBGP Multipath feature was added)

	And additionally for EBGP:

	The path should be learned from an external or confederation-external neighbor (eBGP).
	The IGP metric to the BGP next hop should be equal to the best path's IGP metric.

So I think that the two routes aren't installed because the Neighboring AS
numbers (or the AS-PATH if you have a later IOS) aren't matching.

Cheers,
Lars.
-- 
Lars Fenneberg, lf@elemental.net (private), lf@mcs.de (work)
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