show ip igmp interfaceView the enable status of this feature using the command from EXEC Privilege mode, as shown in the example in Selecting an IGMPVersion.IGMP SnoopingIGMP snooping enables switches to use information in IGMP packets to generate a forwarding table that associates ports withmulticast groups so that when they receive multicast frames, they can forward them only to interested receivers.Multicast packets are addressed with multicast MAC addresses, which represent a group of devices, rather than one unique device.Switches forward multicast frames out of all ports in a virtual local area network (VLAN) by default, even though there may be onlysome interested hosts, which is a waste of bandwidth.If you enable IGMP snooping on a VLT unit, IGMP snooping dynamically learned groups and multicast router ports are made to learnon the peer by explicitly tunneling the received IGMP control packets.IGMP Snooping Implementation Information• IGMP snooping on Dell Networking OS uses IP multicast addresses not MAC addresses.• IGMP snooping is supported on all stack members.• IGMP snooping reacts to spanning tree protocol (STP) and multiple spanning tree protocol (MSTP) topology changes by sendinga general query on the interface that transitions to the forwarding state.• If IGMP snooping is enabled on a PIM-enabled VLAN interface, data packets using the router as an Layer 2 hop may be dropped.To avoid this scenario, Dell Networking recommends that users enable IGMP snooping on server-facing end-point VLANs only.Configuring IGMP SnoopingConfiguring IGMP snooping is a one-step process. To enable, view, or disable IGMP snooping, use the following commands.There is no specific configuration needed for IGMP snooping with virtual link trunking (VLT). For information about VLTconfigurations, refer to Virtual Link Trunking (VLT).• Enable IGMP snooping on a switch.CONFIGURATION modeip igmp snooping enable• View the configuration.CONFIGURATION modeshow running-config• Disable snooping on a VLAN.INTERFACE VLAN modeno ip igmp snoopingRelated Configuration Tasks• Removing a Group-Port Association• Disabling Multicast Flooding• Specifying a Port as Connected to a Multicast Router• Configuring the Switch as QuerierExample of ip igmp snooping enable CommandDell(conf)#ip igmp snooping enableDell(conf)#do show running-config igmpip igmp snooping enableDell(conf)#356 Internet Group Management Protocol (IGMP)
