1050 BigIron RX Series Configuration Guide53-1001810-01Enabling IP multicast traffic reduction41Enabling IP multicast traffic reductionBy default, the BigIron RX forwards all IP multicast traffic out all ports except the port on which thetraffic was received. To reduce multicast traffic through the device, you can enable IP MulticastTraffic Reduction. This feature configures the device to forward multicast traffic only on the portsattached to multicast group members, instead of forwarding all multicast traffic to all ports. Thedevice determines the ports that are attached to multicast group members based on entries in theIGMP table. Each entry in the table consists of MAC addresses and the ports from which the devicehas received Group Membership reports for that group.By default, the device broadcasts traffic addressed to an IP multicast group that does not have anyentries in the IGMP table. When you enable IP Multicast Traffic Reduction, the device determinesthe ports that are attached to multicast group members based on entries in the IGMP table. TheIGMP table entries are created when the VLAN receives a group membership report for a group.Each entry in the table consists of an IP multicast group address and the ports from which thedevice has received Group Membership reports.When the device receives traffic for an IP multicast group, the device looks in the IGMP table for anentry corresponding to that group. If the device finds an entry, the device forwards the group trafficout the ports listed in the corresponding entries, as long as the ports are members of the sameVLAN. If the table does not contain an entry corresponding to the group or if the port is a memberof the default VLAN, the device broadcasts the traffic.NOTEWhen one or more BigIron RX devices are running Layer 2 IP Multicast Traffic reduction, configureone of the devices for active IGMP and leave the other devices configured for passive IGMP. However,if the IP multicast domain contains a multicast-capable router, configure all the BigIron RX devicesfor passive IGMP and allow the router to actively send the IGMP queries.To enable IP Multicast Traffic Reduction, enter the following command.BigIron RX(config)# ip multicast acitiveSyntax: [no] ip multicast active | passiveWhen you enable IP multicast on a BigIron RX, all ports on the device are configured for IGMP.If you are using active IGMP, all ports can send IGMP queries and receive IGMP reports. If you areusing passive IGMP, all ports can receive IGMP queries.IP Multicast Traffic Reduction cannot be disabled on individual ports of a BigIron RX. IP MulticastTraffic Reduction can be disabled globally by entering the no ip multicast command.To disable IP Multicast Traffic Reduction and IGMP snooping, enter the following command.BigIron RX(config)# no ip multicast activeSyntax: [no] ip multicastNOTEIf the "route-only" feature is enabled on the BigIron RX, then IP Multicast Traffic Reduction will notbe supported.Also, this feature is not supported on the default VLAN of the BigIron RX.
