3-2Figure 3-2 Sub-VLAN-based multicast VLANSource Router AIGMP querierVLAN 2VLAN 3VLAN 4Switch AReceiverHost AReceiverHost BReceiverHost CMulticast packetsVLAN 2VLAN 3VLAN 4VLAN 10 (Multicast VLAN)After the configuration, IGMP Snooping manages router ports in the multicast VLAN and member portsin the sub-VLANs. When forwarding multicast data to Switch A, Router A needs to send only one copyof multicast traffic to Switch A in the multicast VLAN, and Switch A distributes the traffic to the multicastVLAN’s sub-VLANs that contain receivers.Port-based multicast VLANAs shown in Figure 3-3, Host A, Host B and Host C are in three different user VLANs. All the user ports(ports with attached hosts) on Switch A are hybrid ports. On Switch A, configure VLAN 10 as amulticast VLAN, assign all the user ports to this multicast VLAN, and enable IGMP Snooping in themulticast VLAN and all the user VLANs.Figure 3-3 Port-based multicast VLANAfter the configuration, upon receiving an IGMP message on a user port, Switch A tags the messagewith the multicast VLAN ID and relays it to the IGMP querier, so that IGMP Snooping can uniformlymanage the router ports and member ports in the multicast VLAN. When forwarding multicast data toSwitch A, Router A needs to send only one copy of multicast traffic to Switch A in the multicast VLAN,and Switch A distributes the traffic to all the member ports in the multicast VLAN.
