question concerning traceroute?

Fri Oct 18 00:47:01 UTC 2002

On Thu, Oct 17, 2002 at 10:31:12AM -0400, Darrell Carley <darrell at 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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