Application Examples - Dell PowerConnect B-RX Configuration Manual

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PIM SM traffic snooping
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 examples

Figure 136
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.
FIGURE 136
When PIM SM traffic snooping is enabled, the device starts listening for PIM SM join and prune
messages and IGMP group membership reports. Until the device receives a PIM SM join message
or an IGMP group membership report, the device forwards IP multicast traffic out 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 IGMP reports
were received.
In this example, the router connected to the receiver for group 239.255.162.1 sends a join
message toward the group's source. 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 receiver's router. The next time the device receives traffic
for 239.255.162.1 from the group's source, the device forwards the traffic only on port 5/1, since
that is the only port connected to a receiver for the group.
1056
shows an example application of the PIM SM traffic snooping feature. In this example, a
PIM SM traffic reduction in enterprise network
The switch snoops for PIM SM join
and prune messages.
The switch detects a source on port1/1
and a receiver for that source's group
on port5/1. It then forwards multicast
data from the source on port1/1
out port5/1 only, which has the receiver.
Without PIM SM traffic reduction, the
switch would forward traffic from the
source out all other ports in the VLAN.
VLAN 2
Port5/1
Router sends a
PIM SM join message
Router
for 239.255.162.1.
Client
Receiver for Group
239.255.162.1
VLAN 2
Port1/1
VLAN 2
Port7/1
10.10.10.6
10.10.10.7
Client sends an
IGMP group
Client
membership report
for 239.255.162.69.
Receiver for Group
30.30.30.6
239.255.162.69
Source for Groups
239.255.162.1
239.255.162.69
Router
10.10.10.5 20.20.20.5
Client
BigIron RX Series Configuration Guide
53-1001810-01