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Re: metric 0 vs 'no metric at all'
From: Pierfrancesco Caci <p.caci () seabone net>
Date: Tue, 03 Jan 2006 09:08:36 +0100


:-> "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



-- 


-------------------------------------------------------------------------------
 Pierfrancesco Caci | Network & System Administrator - INOC-DBA: 6762*PFC
 p.caci () seabone net | Telecom Italia Sparkle - http://etabeta.noc.seabone.net/
     Linux paperino 2.4.20 #1 Mon Dec 2 17:02:14 CET 2002 i686 GNU/Linux


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