682 Configuring L2 Multicast FeaturesWhen a packet enters the switch, the destination MAC address is combinedwith the VLAN ID, and a search is performed in the Layer 2 MFDB. If nomatch is found, then the packet is either flooded to all ports in the VLAN ordiscarded, depending on the switch configuration. If a match is found, thenthe packet is forwarded only to the ports that are members of that multicastgroup.You can create multicast bridging groups and specify the ports and LAGs thatare members of each group. This allows L2 multicast traffic to be confined tothe specified group.L2 Multicast Forwarding ModesYou can configure the forwarding mode for each VLAN as one of thefollowing:• Forward Unregistered—Permits the forwarding of multicast frames formulticast groups that have no registrants (no hosts have joined themulticast group). Unregistered multicast streams are flooded on theVLAN. Registered multicast streams are forwarded to ports in the VLANwhere hosts are registered.• Filter Unregistered—Prohibits the forwarding of unregistered multicastframes, while continuing to forward registered multicast frames.Unregistered frames are dropped.• Forward All—Floods all registered and unregistered multicast on theVLAN.What Is IP Multicast Traffic?IP multicast traffic is traffic that is destined to a host group. Host groups areidentified by class D IP addresses, which range from 224.0.0.0 to239.255.255.255.When a packet with a broadcast or multicast destination IP address isreceived, the switch will forward a copy into each of the remaining networksegments in accordance with the IEEE MAC Bridge standard. Eventually, thepacket is made accessible to all nodes connected to the network.This approach works well for broadcast packets that are intended to be seen orprocessed by all connected nodes. In the case of multicast packets, however,this approach could lead to less efficient use of network bandwidth,
