[87666] in North American Network Operators' Group
Re: metric 0 vs 'no metric at all'
daemon@ATHENA.MIT.EDU (Pierfrancesco Caci)
Tue Jan 3 03:09:26 2006
To: nanog@merit.edu
Reply-To: Pierfrancesco Caci <p.caci@seabone.net>
From: Pierfrancesco Caci <p.caci@seabone.net>
Date: Tue, 03 Jan 2006 09:08:36 +0100
In-Reply-To: <20060103072143.GA14342@shekinah.ip.tiscali.net> (Alexander
Koch's message of "Tue, 3 Jan 2006 08:21:43 +0100")
Errors-To: owner-nanog@merit.edu
:-> "Alexander" == Alexander Koch <efraim@clues.de> writes:
> Hiya,
> I was wondering if someone had done any or some research on
> this before... basically I am not sure with all the many
> implementations of BGP and all the vendors if and what those
> will do when they see a metric of 0 and no metric. I am not
> an expert knowing the actual protocol's messages exchanged,
> but I see some routes with nothing in the metric field on
> the various show commands, and some have explicit '0' metric.
> I do not trust all the BGP implementations around, and we
> consider changing the default outbound, with MEDs of course
> still available on request.
Cisco has a knob for this:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123tcr/123tip2r/ip2_b1gt.htm#wp1076618
default is treating missing med as 0, which tends to surprise peers/customers
who want to send med only on a few routes (i.e., if you want to set a
med on a route, always set it on all your bgp sessions, because you
can't tell if your neighbor has set "missing-as-worst" or not).
Pf
> Alexander
--
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Pierfrancesco Caci | Network & System Administrator - INOC-DBA: 6762*PFC
p.caci@seabone.net | Telecom Italia Sparkle - http://etabeta.noc.seabone.net/
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