Operation Manual – Multicast ProtocolH3C S3610&S5510 Series Ethernet Switches Chapter 5 IGMP Configuration5-1Chapter 5 IGMP Configuration5.1 IGMP OverviewAs a TCP/IP protocol responsible for IP multicast group member management, theInternet Group Management Protocol (IGMP) is used by IP hosts to establish andmaintain their multicast group memberships to immediately neighboring multicastrouters.5.1.1 IGMP VersionsSo far, there are three IGMP versions:z IGMPv1 (described in RFC 1112)z IGMPv2 (described in RFC 2236)z IGMPv3 (described in RFC 3376)All IGMP versions support the Any-Source Multicast (ASM) model. In addition, IGMPv3provides strong support to the Source-Specific Multicast (SSM) model.5.1.2 Work Mechanism of IGMPv1IGMPv1 manages multicast groups mainly based on the query and responsemechanism.Of multiple multicast routers on the same subnet, only one router is needed for sendingIGMP queries because all the routers can receive IGMP reports from hosts. So, aquerier election mechanism is required to determine which router will act as the IGMPquerier on the subnet.In IGMPv1, the designated router (DR) elected by the Layer 3 multicast routing protocol(such as PIM) serves as the IGMP querier.For more information about a DR, refer to ” PIM Configuration”.
