Reference Guide

Figure 13. IGMP Membership Reports: Joining and Filtering

Leaving and Staying in Groups

The below illustration shows how multicast routers track and refreshes the state change in response to

group-and-specific and general queries.

• Host 1 sends a message indicating it is leaving group 224.1.1.1 and that the included filter for 10.11.1.1

and 10.11.1.2 are no longer necessary.

• The querier, before making any state changes, sends a group-and-source query to see if any other

host is interested in these two sources; queries for state-changes are retransmitted multiple times. If

any are interested, they respond with their current state information and the querier refreshes the

relevant state information.

• Separately in the below figure, the querier sends a general query to 224.0.0.1.

• Host 2 responds to the periodic general query so the querier refreshes the state information for that

group.

Internet Group Management Protocol (IGMP)