Dell POWEREDGE M1000E - Manual (Page 714)

714 Configuring L2 Multicast Features
When a packet enters the switch, the destination MAC address is combined
with the VLAN ID, and a search is performed in the Layer 2 MFDB. If no
match is found, then the packet is either flooded to all ports in the VLAN or
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.