Brocade Multi-Service IronWare Multicast Configuration Guide (Supporting R05.6.00) - Manual (Page 207)

Multi-Service IronWare Multicast Configuration Guide 195
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IPv6 Multicast Listener Discovery snooping
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PIM-SM traffic snooping eliminates the superfluous traffic by configuring the device to forward IPv6
multicast group traffic only on the ports that are attached to receivers for the group.
PIM-SM traffic snooping requires IPv6 Multicast Traffic Reduction to be enabled on the device. IPv6
Multicast Traffic Reduction configures the device to listen for MLD messages. PIM-SM traffic
snooping provides a finer level of multicast traffic control by configuring the device to listen
specifically for PIM-SM join and prune messages sent from one PIM-SM router to another through
the device.
Application examples
Figure 21 shows an example application of the PIM-SM traffic snooping feature. In this example, a
device is connected through an IP router to a PIM-SM group source that is sending traffic for two
PIM-SM groups. The device also is connected to a receiver for each of the groups.
NOTE
PIM-SM traffic snooping applies only to PIM-SM version 2 (PIM V2).
FIGURE 21 PIM-SM IPv6 traffic reduction in enterprise network
When PIM-SM traffic snooping is enabled, the device starts listening for PIM-SM join and prune
messages and MLD Snooping reports. Until the device receives a PIM-SM join message or an MLD
report, the device forwards IPv6 multicast traffic out to all ports. Once the device receives a join
message or Group Membership report for a group, the device forwards subsequent traffic for that
group only on the ports from which the join messages or MLD reports were received.
In this example, the router connected to the receiver for group ff0e::1 sends a join message toward
the source of the group. Since PIM-SM traffic snooping is enabled on the device, the device
examines the join message to learn the group ID, then makes a forwarding entry for the group ID
and the port connected to the router of the receiver. The next time the device receives traffic for
ff0e::1 from the source of the group, the device forwards the traffic only on port 5/1, because that
is the only port connected to a receiver for the group.