3com 8807 User Guide

C

HAPTER

 39: IGMP S

NOOPING

 C

ONFIGURATION

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IGMP leave message: Transmitted from the multicast group member to the 
multicast router to notify that a host left the multicast group. When received a 
leave message of an IP multicast group, the Ethernet switch transmits the 
specific query message concerning that group to the port received the 
message, in order to check if the host still has some other member of this 
group and meanwhile starts a maximum response timer. If the switch has not 
receive any report message from the multicast group after the timer expires, 
the port will be removed from the corresponding MAC multicast group. If the 
MAC multicast group does not have any member, the switch will notify the 
multicast router to remove the branch from the multicast tree.

The main IGMP Snooping configuration includes:

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Among the above configuration tasks, enabling IGMP Snooping is required, while 
others are optional for your requirements.

You can use the following commands to enable/disable IGMP Snooping to control 
whether MAC multicast forwarding table is created and maintained on Layer 2.

Perform the following configuration in system view and VLAN view.

By default, IGMP Snooping is disabled.

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First enable IGMP Snooping globally in system view, and then enable IGMP 
Snooping in VLAN view. Otherwise, IGMP Snooping will not take effect.

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Although layer 2 and layer 3 multicast protocols can be configured in pair, they 
cannot run on the same VLAN or its corresponding VLAN interface at the same 
time. For example, if PIM or IGMP is enabled on a VLAN, then IGMP Snooping 
cannot operate on this VLAN.

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If the VLAN VPN is enabled on a port, the IGMP Snooping feature cannot be 
enabled on the VLAN for the port or the IGMP feature cannot be enabled on 
the corresponding VLAN interface.

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If IGMP Snooping feature is enabled on a VLAN, or IGMP is enabled on the 
VLAN interface, you cannot add the member port on which VLAN VPN is 
enabled into the VLAN.

Table 411   Enable/Disable IGMP Snooping

Enable/disable IGMP Snooping 

igmp-snooping { enable | disable }