Configuring Pim Snooping; Overview - HP FlexFabric 5950 series Configuration Manual

Configuring PIM snooping

Overview

PIM snooping runs on Layer 2 devices. It works with IGMP snooping to analyze received PIM
messages, and adds the ports that are interested in specific multicast data to a PIM snooping routing
entry. In this way, the multicast data can be forwarded to only the ports that are interested in the data.
Figure 20 Multicast packet transmission without or with PIM snooping
Multicast packet transmission
when only IGMP snooping runs
Source 1
PIM
router 1
PIM
router 3
Receiver 1
As shown in
multicast data to multicast group G2. Receiver 1 belongs to G1, and Receiver 2 belongs to G2. The
Layer 2 switch's interfaces that connect to the PIM routers are in the same VLAN or VSI.
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When the Layer 2 switch runs only IGMP snooping, it performs the following actions:
a. Maintains the router ports according to the received PIM hello messages that PIM routers
send.
b. Floods all other types of received PIM messages except PIM hello messages in the VLAN
or VSI.
c. Forwards all multicast data to all router ports in the VLAN or VSI.
Source 2
router 2
Layer 2 switch
router 4
Receiver 2
Multicast packets (S1, G1)
Multicast packets (S2, G2)
Figure 20, Source 1 sends multicast data to multicast group G1, and Source 2 sends
IGMP snooping and PIM snooping both run
Source 1
PIM PIM
router 1
PIM PIM
router 3
Receiver 1
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Multicast packet transmission when
Layer 2 switch
Join message (S1, G1)
Join message (S2, G2)
Source 2
PIM
router 2
PIM
router 4
Receiver 2