3com S7906E Installation Instruction

 

1-2 

Figure 1-1 Before and after IGMP snooping is enabled on the Layer 2 device 

Multicast packet transmission

 without IGMP Snooping

Host A

Host B

Host C

 Multicast packets

Multicast packet transmission

 when IGMP Snooping runs

Host A

Host B

Host C

 

 

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. 

As shown in 

, 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).  

Figure 1-2 IGMP snooping related ports  

Router A

Switch A

Switch B

GE2/0/1

GE2/0/2

GE2/0/3

GE2/0/1

GE2/0/2

Host A

Host B

Host C

Host D

 Multicast packets

Router port

Member port

 

 

Ports involved in IGMP snooping, as shown in 

, are described as follows: