Cisco Systems 3130 User Manual

IGMP snooping functions across the switch stack; that is, IGMP control information from one switch is 
distributed to all switches in the stack. (See 

 for more information 

about switch stacks.) Regardless of the stack member through which IGMP multicast data enters the 
stack, the data reaches the hosts that have registered for that group.

If a switch in the stack fails or is removed from the stack, only the members of the multicast group that 
are on that switch will not receive the multicast data. All other members of a multicast group on other 
switches in the stack continue to receive multicast data streams. However, multicast groups that are 
common for both Layer 2 and Layer 3 (IP multicast routing) might take longer to converge if the stack 
master is removed.

IGMP snooping allows switches to examine IGMP packets and make forwarding decisions based on their 
content. These sections contain this configuration information:

 shows the default IGMP snooping configuration.

IGMP snooping

Enabled globally and per VLAN

Multicast routers

None configured

Multicast router learning (snooping) method

PIM-DVMRP

IGMP snooping Immediate Leave

Disabled

Static groups

None configured

TCN

1

 flood query count

2

TCN query solicitation

Disabled