IGMP v2 Timer

The following timer(1-3) are configurable in the Cisco router under the interface.

1. Query interval: (ip igmp query-interval)
A time period between General Queries sent by a router. Cisco default is 60 sec. (RFC is 125 sec)

2. Query Response Interval: (ip igmp max-response-time)
The maximum response time (MRT) for hosts to respond to the periodic general Queries. Default is 10 sec. MRT timer to suppress many of the unnecessary IGMP reports. Report suppression is when a host receives a report sent by another host for the same mcast group for which it is planning to send a report, host does not send. 3 second MRT is expressed as 30.

3. Other Querier Present Interval (RFC) or Querier Timeout (Cisco)
To configure the timeout period before the router triggers Internet Group Management Protocol (IGMP) querier reelection for the interface, use the ip igmp querier-timeout command in interface configuration mode. To restore the default value, use the no form of this command.

4. Last Member Query Interval and Last Member Query Count
These values determine how long it takes a router to believe that all hosts on a LAN have left a particular group. By default, routers use an MRT of 10 (1 second) for Group-Specific Queries; because a router should receive a response to a Group-Specific Query in that amount of time, the router uses the MRT value as the value of the Last Member Query Interval. So, the router uses the following process:
1). Send a Group-Specific Query in response to an IGMP Leave.
2). If no Report is received within the Last Member Query Interval, repeat Step 1.
3). Repeat Step 1 the number of times defined by the value of the Last Member Query Count.
The Last Member Query Count is the number of consecutive Group-Specific Queries sent for the same group before the router concludes that there are no active members of the group on a subnet.
The default value for the Last Member Query Count is 2. So, the leave latency is typically less than 3 seconds, compared to up to 3 minutes with IGMPv1.
ip igmp last-member-query-count
ip igmp last-member-query-interval


The following ones are not configurable.
1. Group Membership Interval
The Group Membership Interval is the amount of time that must pass before a multicast router decides there are no more members of a group on a network. This value MUST be ((the Robustness Variable) times (the Query Interval)) plus (one Query Response Interval).