The BEB acts as the IGMP Querier and creates tables for links that need IP multicast streams. IGMP and IGMP Snooping cannot work without an IGMP Querier that sends out periodic IGMP queries.
The BEB only interacts with IGMP messages and not PIM. All multicast traffic must enter the BEB for the data stream to be announced.
The BEB must be the only IGMP Querier in the VLAN. If the BEB receives an IGMP query from any other device, unexpected behavior results, including traffic loss.
The IGMP query message is an IP packet and requires a source IP address. However, Layer 2 IGMP Snooping with SPBM by default turns on the service without the configuration of an IP address on the VLAN. By default, the BEB sends an IGMP query message with an IP source address of 0.0.0.0. If there are interoperability issues with third party vendors as a result of the 0.0.0.0 IP address, then you can configure the querier address under IGMP, without having to configure an IP address for the Layer 2 VSN VLAN.
IGMP Snooping, operating on the Layer 2 VSN, listens to conversations between hosts and routers, and maintains a table for links that need IP multicast streams.
For IGMP Snooping, ensure that the IGMP version used by multicast hosts and other devices in the network is the same as the IGMP version configured on the IGMP Snooping VLAN, or that you enable compatibility mode.
For more conceptual and configuration information on IGMP, see IP Multicast.