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Re: looping traceroutes
From: "Patrick W. Gilmore" <patrick () ianai net>
Date: Wed, 19 Sep 2001 00:40:55 -0400


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


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