2.2.a [iii] IGMP querier
When there is no multicast router in the VLAN to originate the queries, you must configure an IGMP snooping querier to send membership queries. When an IGMP snooping querier is enabled, it sends out periodic IGMP queries that trigger IGMP report messages from hosts that want to receive IP multicast traffic. IGMP snooping listens to these IGMP reports to establish appropriate forwarding.
Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 2053-2055). . Kindle Edition.