2-15z One port can belong to only one multicast VLAN.z The port connected to a user terminal must be a hybrid port.z The multicast member ports must be in the same VLAN with the router port. Otherwise, themulticast member port cannot receive multicast packets.z If a router port is in a multicast VLAN, the router port must be configured as a trunk port or a hybridport that allows tagged packets to pass for the multicast VLAN. Otherwise, all the multicastmember ports in this multicast VLAN cannot receive multicast packets.z When the multicast VLAN is set up, all IGMP report messages are forwarded to the router ports inthe multicast VLAN. If no router ports exist in the multicast VLAN, all IGMP report messages areflooded within the multicast VLAN.Displaying and Maintaining IGMP SnoopingAfter the configuration above, you can execute the following display commands in any view to verifythe configuration by checking the displayed information.You can execute the reset command in user view to clear the statistics information about IGMPSnooping.Table 2-21 Display and maintain IGMP SnoopingOperation Command RemarksDisplay the current IGMPSnooping configurationdisplay igmp-snoopingconfigurationDisplay IGMP Snoopingmessage statisticsdisplay igmp-snoopingstatisticsDisplay the information aboutIP and MAC multicast groups inone or all VLANsdisplay igmp-snoopinggroup [ vlan vlanid ]You can execute the displaycommands in any view.Clear IGMP Snooping statistics reset igmp-snoopingstatisticsYou can execute the resetcommand in user view.IGMP Snooping Configuration ExamplesConfiguring IGMP SnoopingNetwork requirementsTo prevent multicast traffic from being flooded at Layer 2, enable IGMP snooping on Layer 2 switches.z As shown in Figure 2-3, Router A connects to a multicast source (Source) throughGigabitEthernet1/0/2, and to Switch A through GigabitEthernet1/0/1.z Run PIM-DM and IGMP on Router A. Run IGMP snooping on Switch A. Router A acts as the IGMPquerier.z The multicast source sends multicast data to the multicast group 224.1.1.1. Host A and Host B arereceivers of the multicast group 224.1.1.1.
