• Statically specify a port in a VLAN as connected to a multicast router.INTERFACE VLAN modeip igmp snooping mrouter• View the ports that are connected to multicast routers.EXEC Privilege mode.show ip igmp snooping mrouterConfiguring the Switch as QuerierTo configure the switch as a querier, use the following command.Hosts that do not support unsolicited reporting wait for a general query before sending a membership report. When the multicast sourceand receivers are in the same VLAN, multicast traffic is not routed and so there is no querier. Configure the switch to be the querier for aVLAN so that hosts send membership reports and the switch can generate a forwarding table by snooping.• Configure the switch to be the querier for a VLAN by first assigning an IP address to the VLAN interface.INTERFACE VLAN modeip igmp snooping querierIGMP snooping querier does not start if there is a statically configured multicast router interface in the VLAN.The switch may lose the querier election if it does not have the lowest IP address of all potential queriers on the subnet.When enabled, IGMP snooping querier starts after one query interval in case no IGMP general query (with IP SA lower than its VLAN IPaddress) is received on any of its VLAN members.Adjusting the Last Member Query IntervalTo adjust the last member query interval, use the following command.When the querier receives a Leave message from a receiver, it sends a group-specific query out of the ports specified in the forwardingtable. If no response is received, it sends another. The amount of time that the querier waits to receive a response to the initial query beforesending a second one is the last member query interval (LMQI). The switch waits one LMQI after the second query before removing thegroup-port entry from the forwarding table.• Adjust the last member query interval.INTERFACE VLAN modeip igmp snooping last-member-query-intervalFast Convergence after MSTP Topology ChangesWhen a port transitions to the Forwarding state as a result of an STP or MSTP topology change, Dell Networking OS sends a general queryout of all ports except the multicast router ports. The host sends a response to the general query and the forwarding database is updatedwithout having to wait for the query interval to expire.When an IGMP snooping switch is not acting as a querier, it sends out the general query in response to the MSTP triggered link-layertopology change, with the source IP address of 0.0.0.0 to avoid triggering querier election.Internet Group Management Protocol (IGMP) 363
