North American Network Operators Group
Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: looping traceroutes

  • From: Patrick W. Gilmore
  • Date: Wed Sep 19 00:44:44 2001

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