BigIron RX Series Configuration Guide 65353-1001810-01Configuring IP multicast traffic reduction 23When you enable IP Multicast Traffic Reduction, you also can configure the following features:• IGMP mode – When you enable IP Multicast Traffic Reduction, the device passively listens forIGMP Group Membership reports by default. If the multicast domain does not have a to sendIGMP queries to elicit these Group Membership reports, you can enable the device to activelysend the IGMP queries. The IGMP passive mode is also known as IGMP snooping andfacilitates IP Multicast Traffic Reduction.NOTEA router-id is required if a virtual interface (ve) or IP is not configured for IGMP snooping towork.• Query interval – The query interval specifies how often the device sends Group Membershipqueries. This query interval applies only to the active IGMP mode. The default is 60 seconds.You can change the interval to a value from 10 – 600 seconds.• Age interval – The age interval specifies how long an IGMP group can remain in the IGMP grouptable without the device receiving a Group Membership report for the group. If the age intervalexpires before the device receives another Group Membership report for the group, the deviceremoves the entry from the table. The default is 140 seconds. You can change the interval to avalue from 10 – 1220 seconds.Furthermore, when you enable IP Multicast Traffic Reduction, the device forwards all IP multicasttraffic by default but you can enable the device to do the following:• Forward IP multicast traffic only for groups for which the device has received a GroupMembership report.• Drop traffic for all other groups.The following sections describe how to configure IP multicast traffic reduction and PIM SM TrafficSnooping parameters on a device.Enabling IP multicast traffic reductionBy default, the device 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.
