[42696] in North American Network Operators' Group
Re: looping traceroutes
daemon@ATHENA.MIT.EDU (Patrick W. Gilmore)
Wed Sep 19 00:42:20 2001
Message-Id: <5.1.0.14.2.20010919003918.01c599b0@127.0.0.1>
Date: Wed, 19 Sep 2001 00:40:55 -0400
To: nanog@merit.edu
From: "Patrick W. Gilmore" <patrick@ianai.net>
Cc: Ratul Mahajan <ratul@cs.washington.edu>
In-Reply-To: <Pine.LNX.4.33.0109182130560.25412-100000@krypton.cs.washin
gton.edu>
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At 09:31 PM 9/18/2001 -0700, Ratul Mahajan wrote:
[SNIP]
>28 193.251.133.117 (193.251.133.117) 586.776 ms 584.171 ms 586.944 ms
>29 193.251.133.117 (193.251.133.117) 608.677 ms 610.789 ms 618.232 ms
>30 193.251.133.117 (193.251.133.117) 641.141 ms 643.149 ms 639.050 ms
This sometimes happens when there is a filter on that router. All packets
going through get an ICMP administratively denied sent back, and the
traceroute host interprets that as an ICMP TTL expired or perhaps does not
even notice what type of ICMP it is, just looks at the source IP address.
>27 208.63.128.3 (208.63.128.3) 111.475 ms 69.670 ms 69.267 ms
>28 208.63.128.1 (208.63.128.1) 68.883 ms 67.147 ms 72.106 ms
>29 208.63.128.3 (208.63.128.3) 69.842 ms 67.889 ms 66.944 ms
>30 208.63.128.1 (208.63.128.1) 70.986 ms 73.124 ms 68.452 ms
This looks exactly like a routing loop to me. Why do you think it is not a
routing loop?
--
TTFN,
patrick
