Dell PowerConnect 6248 User's Guide - Page 397

Changing the Bridge Multicast Forwarding Mode. 1. Open the Bridge Multicast Forward page. 2. Select the VLAN ID from the drop-down menu. 3. Select the Forwarding Mode to assign the VLAN from the drop-down menu. 4. Click Apply Changes. The VLAN is updated with the Forwarding Mode setting, and the device is updated. Configuring Bridge Multicast Forwarding Using CLI Commands For information about the CLI commands that perform this function, see the following chapter in the CLI Reference Guide: • Address Table Commands The following table summarizes the equivalent CLI commands for this feature. Table 7-41. Bridge Multicast Forwarding Commands CLI Command bridge multicast forbidden forwardunregistered bridge multicast forward-all bridge multicast forward-unregistered Description Forbids forwarding-unregistered-multicast-addresses. Enables forwarding of all Multicast packets. Enable the forwarding of unregistered multicast addresses. IGMP Snooping Internet Group Management Protocol (IGMP) Snooping is a feature that allows a switch to forward multicast traffic intelligently on the switch. Multicast IP 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. Based on the IGMP query and report messages, the switch forwards traffic only to the ports that request the multicast traffic. This prevents the switch from broadcasting the traffic to all ports and possibly affecting network performance. When a packet with a broadcast or multicast destination 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. Allowing switches to snoop IGMP packets is a creative effort to solve this problem. The switch uses the information in the IGMP packets as they are being forwarded throughout the network to determine which segments should receive packets directed to the group address. Configuring Switching Information 397