[52824] in North American Network Operators' Group
Re: question concerning traceroute?
daemon@ATHENA.MIT.EDU (Lane Patterson)
Thu Oct 17 20:48:23 2002
Date: Thu, 17 Oct 2002 17:47:01 -0700
From: Lane Patterson <lane@laneandmimi.com>
To: Darrell Carley <darrell@national-net.com>
Cc: nanog@merit.edu
In-Reply-To: <000e01c275e9$d7a5c3f0$c701a8c0@sarcasta>
Errors-To: owner-nanog-outgoing@merit.edu
On Thu, Oct 17, 2002 at 10:31:12AM -0400, Darrell Carley <darrell@national-net.com> wrote:
> I am trying to troubleshoot a latency issue for some of our networks,
> and was wondering about this.Knowing that routing isn't always
> symmetrical, is it possible for a traceroute to traverse a different
> reverse path, than the path that it took to get there? .or will it
> provide a trace of the path the packet took to reach the destination?
> According to definition, is should take the same path, but are there any
> other cases that I should be aware of?
Something else to be aware of is the effect of ECMP on traceroutes--where
the source/dest IP (among other hash inputs) can impact which of several
parallel equal cost paths you take thru a backbone. ECMP is fairly common,
so I would suspect a fairly large percentage of paths are subject to it.
-Lane
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> Darrell
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