From owner-freebsd-questions  Mon Sep 18 23: 7:45 2000
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Date: Mon, 18 Sep 2000 23:07:22 -0700
From: "Crist J . Clark" <cjclark@reflexnet.net>
To: Elliot Finley <lists@efinley.com>
Cc: isp-tech@isp-tech.com, freebsd-questions@FreeBSD.ORG
Subject: Re: How do I interpret this traceroute?
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On Tue, Sep 19, 2000 at 05:28:13AM +0000, Elliot Finley wrote:
> [lines wrapped at 110 so that traceroute output will not be wrapped]

Please still wrap your written text at about 72.

> The first traceroute dies at 157.130.162.62.  The !H means host unreachable.  But does this mean that
> 216.190.63.1 (the final destination) is the one that is having problems, and is unreachable?  Or does this
> mean that there is some sort of routing loop on 157.130.162.62?
> 
> The second traceroute makes it all the way through and is just shown here for reference.
[snip]

Remember how a traceroute works. Packets are getting to 157.130.162.62
with a TTL of zero so it responds with time-to-live expired
messages. That is the 'successful' traceroute step. Next, your machine
dials up the TTL. Now 157.130.162.62 atcually tries to route the
packets (it did not try before since they had expired anyway) and
realizes the host is unreachable. It responds with the ICMP message
and you see '!H.'

There is not enough to diagnose the problem. It could be trouble at
the router or at the destination host.
-- 
Crist J. Clark                           cjclark@alum.mit.edu


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