6-10Configuring IGMP Snooping QuerierIn an IP multicast network running IGMP, a multicast router is responsible for sending IGMP generalqueries, so that all Layer 3 multicast devices can establish and maintain multicast forwarding entries,thus to forward multicast traffic correctly at the network layer. This router or Layer 3 switch is calledIGMP querier.However, a Layer 2 multicast switch does not support IGMP, and therefore cannot send general queriesby default. By enabling IGMP Snooping querier on a Layer 2 switch in a VLAN where multicast trafficneeds to be Layer-2 switched only and no multicast routers are present, the Layer 2 switch will act as aquerier to send IGMP general queries, thus allowing multicast forwarding entries to be established andmaintained at the data link layer.You can also configure the source address and interval of general queries to be sent from the IGMPSnooping querier.Follow these steps to configure IGMP Snooping querier:To do... Use the command... RemarksEnter system view system-view —Enable IGMP Snooping igmp-snooping enableRequiredBy default, IGMP Snooping isdisabled.Enter VLAN view vlan vlan-id —Enable IGMP Snooping igmp-snooping enableRequiredBy default, IGMP Snooping isdisabled.Enable IGMP Snoopingquerier igmp-snooping querierRequiredBy default, IGMP Snoopingquerier is disabled.Configure the intervalbetween IGMP generalqueriesigmp-snooping query-intervalsecondsOptionalBy default, the interval betweenIGMP general queries is 60seconds.Configure the source IPaddress of IGMP generalqueriesigmp-snooping general-querysource-ip { current-interface |ip-address }OptionalBy default, the source IP addressof IGMP general queries is0.0.0.0.Suppressing Flooding of Unknown Multicast Traffic in a VLANWith IGMP Snooping enabled in a VLAN, multicast traffic for unknown multicast groups is flooded withinthe VLAN by default. This wastes network bandwidth and affects multicast forwarding efficiency.With the unknown multicast flooding suppression function enabled, when receiving a multicast packetfor an unknown multicast group, an IGMP Snooping switch creates a nonflooding entry and relays thepacket to router ports only, instead of flooding the packet within the VLAN. If the switch has no routerports, it drops the multicast packet.Follow these steps to suppress flooding of unknown multicast traffic in the VLAN:
