2.2.a [ii] IGMP snooping
IGMP snooping is a feature that allows the switch to snoop or listen in on the IGMP conversation between hosts and routers. When a switch hears an IGMP report from a host for a given multicast group, the switch adds the host’s port number to the GDA list for that group. And, when the switch hears an IGMP Leave, it removes the host’s port from the CAM table entry.
Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 2049-2051). . Kindle Edition.