IGMPv2 Querier Timer Confusion

Hi all,

I am wondering if anyone can provide some clarification on IGMPv2 timers? 

I specifically refer to the CCIE R&S OCG (4th Edition) and how it appears that the timers talked about vary to other sources.

 

If we look at the output from the sh ip igmp interface command, we see the following:

IGMP query interval is 60 seconds

  IGMP querier timeout is 120 seconds

  IGMP max query response time is 10 seconds

  Last member query count is 2

  Last member query response interval is 1000 ms

 

Now, where I am struggling to make a connection is relating to the Querier timers.

So, the OCG states:

 

When the elected querier does not send a query for two consecutive Query Intervals plus on half of one Query Response Interval, it is considered to be dead, and a new querier is elected. RFC 2236 referred to this time interval as the Other Querier Present Interval. The default value for the Other Querier Present Interval is 255 seconds, because the default General IGMPv2 Query Interval is 125 seconds and the default Query Response Interval is 10 seconds.

I guess the image below shows where the figures should match up in the different sources.

Going off the book text, I would expect to see the querier timeout listed as 125 seconds, not 120 seconds and I would also expect the book to show 125 instead of 125 seconds for the Other Querier Present Interval (however, is this specifically an RFC figure and 125 is the equivalent on IOS?)

 

image

 

 

Any help would be appreciated. Been going over this and for some reason (as small of a detail as it is), I cannot get this straight in my head.

 

 

Thanks

Sign In or Register to comment.