Re: [nsp] BGP4 Route Selection Criteria

From: Tony Tauber (ttauber@bbnplanet.com)
Date: Mon Nov 22 1999 - 16:38:02 EST


On Mon, 22 Nov 1999, Jay Stewart wrote:

> Can someone send me the route selection criteria that BGP4 uses to
> determine which route is most preferrable?
>
> From my understanding, all things being equal, a shorter AS-Path will
> be chosen, regardless of the length of the prefix. In other words, if
> I advertise 10.0.0.0/8 with as path - {AS1 AS2}, and I advertise
> 10.0.10.0/24 with as path prepending as such - {AS1 AS2 AS2}, will
> remote routers select the longer AS Path route due to the shorter
> prefix?

No, no, no. Longest match always wins. Always.
This fact holds true for routing in general.

Tony



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