H3C Technologies H3C S7500E Series Switches - Manual (Page 34)

2-2
Figure 2-1 Before and after IGMP snooping is enabled on the Layer 2 device
Multicast packet transmission
without IGMP Snooping
Source
Multicast router
Host A
Receiver
Host B
Host C
Receiver
Multicast packets
Layer 2 switch
Multicast packet transmission
when IGMP Snooping runs
Source
Multicast router
Host A
Receiver
Host B
Host C
Receiver
Layer 2 switch
IGMP snooping forwards multicast data to only the receivers requiring it at Layer 2. It brings the
following advantages:
z Reducing Layer 2 broadcast packets, thus saving network bandwidth.
z Enhancing the security of multicast traffic.
z Facilitating the implementation of per-host accounting.
Basic Concepts in IGMP Snooping
IGMP Snooping related ports
As shown in Figure 2-2 , Router A connects to the multicast source, IGMP snooping runs on
Switch A and Switch B, and Host A and Host C are receiver hosts (namely, multicast group
members).