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PowerConnect B-Series FCX Configuration Guide 653
53-1002266-01
PIM SM traffic snooping overview
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VLAN specific configuration
You can configure IGMP snooping on some VLANs or on all VLANs. Each VLAN can be
independently enabled or disabled for IGMP snooping, and can be configured for IGMPv2 or
IGMPv3. In general, the ip multicast commands apply globally to all VLANs except those configured
with VLAN-specific multicast commands. The VLAN-specific multicast commands supersede the
global ip multicast commands.
Using IGMPv2 with IGMPv3
IGMP snooping can be configured for IGMPv2 or IGMPv3 on individual ports on a VLAN. An
interface or router sends the queries and reports that include its IGMP version specified on it. The
version configuration only applies to sending queries. The snooping device recognizes and
processes IGMPv2 and IGMPv3 packets regardless of the version configuration.
To avoid version deadlock, an interface retains its version configuration even when it receives a
report with a lower version.
PIM SM traffic snooping overview
When multiple PIM sparse routers connect through a snooping-enabled device, the device always
forwards multicast traffic to these routers. For example, PIM sparse routers R1, R2, and R3
connect through a device. Assume R2 needs traffic, and R1 sends it to the device, which forwards
it to both R2 and R3, even though R3 does not need it. A PIM snooping-enabled device listens to
join and prune messages exchanged by PIM sparse routers, and stops traffic to the router that
sends prune messages. This allows the device to forward the data stream to R2 only.
PIM SM traffic snooping requires IP multicast traffic reduction to be enabled on the device. IP
multicast traffic reduction configures the device to listen for IGMP 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.
NOTE
This feature applies only to PIM SM version 2 (PIM V2).
Application example
Figure 114 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.