704 Configuring L2 Multicast Features
discarded, depending on the switch configuration. If a match is found, then 
the packet is forwarded only to the ports that are members of that multicast 
group.
You can create multicast bridging groups and specify the ports and LAGs that 
are members of each group. This allows L2 multicast traffic to be confined to 
the specified group.
You can configure the forwarding mode for each VLAN as one of the 
following:
• Forward Unregistered—Permits 
control
 multicast frames to be forwarded. 
This means that multicast streams that have no registrants (no hosts have 
joined the multicast group) will be flooded.
• Filter Unregistered—Prohibits the forwarding of 
control
 multicast frames 
such as router advertisements, RIP, and OSPF. 
• Forward All—Permits registered and unregistered multicast packets to 
forward. 
What Is IP Multicast Traffic?
IP multicast traffic is traffic that is destined to a host group. Host groups are 
identified by class D IP addresses, which range from 224.0.0.0 to 
239.255.255.255. 
When a packet with a broadcast or multicast destination IP address is 
received, the switch will forward a copy into each of the remaining network 
segments in accordance with the IEEE MAC Bridge standard. Eventually, the 
packet is made accessible to all nodes connected to the network.
This approach works well for broadcast packets that are intended to be seen or 
processed by all connected nodes. In the case of multicast packets, however, 
this approach could lead to less efficient use of network bandwidth, 
particularly when the packet is intended for only a small number of nodes. 
Packets will be flooded into network segments where no node has any interest 
in receiving the packet.