H3C Technologies H3C S12500 Series Switches - Manual (Page 29)

13
Configuring IGMP snooping
Overview
IGMP snooping runs on a Layer 2 switch as a multicast constraining mechanism to improve multicast
forwarding efficiency. It creates Layer 2 multicast forwarding entries from IGMP packets that are
exchanged between the hosts and the router.
As shown in
Figure 11 , when IGMP snooping is not enabled, the Layer 2 switch floods multicast packets
to all hosts. When IGMP snooping is enabled, the Layer 2 switch forwards multicast packets of known
multicast groups to only the receivers.
The term "router" in this document refers to both routers and Layer 3 switches.
Figure 11 Before and after IGMP snooping is enabled on the Layer 2 device
Basic IGMP snooping concepts
IGMP snooping related ports
As shown in Figure 12 , IGMP snooping runs on Device A and Device B, and Host A and Host C are
receivers in a multicast group.