2-4
group-specific query, a switch forwards it through all the router ports in the VLAN and all member ports
of that multicast group, and performs the following to the receiving port:
z If any IGMP report in response to the group-specific query arrives to the member port before its
aging timer expires, this means that some other members of that multicast group still exist under
that port: the switch resets the aging timer of the member port.
z If no IGMP report in response to the group-specific query arrives to the member port before its
aging timer expires as a response to the IGMP group-specific query, this means that no members
of that multicast group still exist under the port: the switch deletes the forwarding entry
corresponding to the port from the forwarding table when the aging timer expires.
After an Ethernet switch enables IGMP Snooping, when it receives the IGMP leave message sent by a
host in a multicast group, it judges whether the multicast group exists automatically. If the multicast
group does not exist, the switch drops this IGMP leave message.
IGMP Snooping Configuration
The following table lists all the IGMP Snooping configuration tasks:
Table 2-2 IGMP Snooping configuration tasks
Operation Remarks
Enabling IGMP Snooping Required
Configuring the Version of IGMP Snooping Optional
Configuring Timers Optional
Configuring Fast Leave Processing Optional
Configuring a Multicast Group Filter Optional
Configuring the Maximum Number of Multicast Groups on a Port Optional
Configuring IGMP Snooping Querier Optional
Suppressing Flooding of Unknown Multicast Traffic in a VLAN Optional
Configuring Static Member Port for a Multicast Group Optional
Configuring a Static Router Port Optional
Configuring a Port as a Simulated Group Member Optional
Configuring a VLAN Tag for Query Messages Optional
Configuring Multicast VLAN Optional
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