Wireshark-dev: [Wireshark-dev] Cisco ip igmp query-max-response-time
From: Christopher Maynard <christopher.maynard@xxxxxxxxx>
Date: Fri, 13 Apr 2012 18:21:03 +0000 (UTC)
One of the Cisco IOS IP commands is "ip igmp query-max-response-time", described here: http://www.cisco.com/en/US/docs/ios/12_2/ipmulti/command/reference/1rfmult1.html#wp1018684. The range of values one can use is not listed, but it is (or at least was the last time I checked) 1-25. Some time ago, a colleague & I discovered empirically what each value in the range of 1-25 actually corresponds to in real time. It was a simple matter of setting it to each value in the range of 1-25 and then examining the value of the Max Response Time field of the IGMP query packet (See http://tools.ietf.org/html/rfc2236#section-2.2). For the 1st 12 values, it's 1-1, but then it increases exponentially. Here's the full table: query-max-response-time actual response time (seconds) 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10 11 11 12 12 13 14.4 14 22.4 15 35.2 16 51.2 17 83.2 18 128 19 192 20 307.2 21 460.8 22 716.8 23 1126.4 24 1638.4 25 2662.4 I don't remember the exact version of IOS we tested with, and I don't know if this behavior was intentional or not on the part of Cisco or if it was a bug that was corrected in later versions or what. I just thought that for anyone using this command, this information might be useful to you, particularly when using values above 12. If anyone thinks this information is useful, it could be added to http://wiki.wireshark.org/IGMP. Well, for what it's worth ... - Chris
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