2-6Table 2-2 describes how an IGMP snooping proxy processes IGMP messages.Table 2-2 IGMP message processing on an IGMP snooping proxyIGMP message ActionsGeneral queryWhen receiving an IGMP general query, the proxy forwards it to all ports but thereceiving port. In addition, the proxy generates a report according to the groupmemberships it maintains and sends the report out all router ports.Group-specificqueryIn response to the IGMP group-specific query for a certain multicast group, theproxy sends the report to the group out all router ports if the forwarding entry forthe group still contains a member port.ReportWhen receiving a report for a multicast group, the proxy looks up the multicastforwarding table for the entry for the multicast group. If the forwarding entry isfound with the receiving port contained as a dynamic member port in the outgoingport list, the proxy resets the aging timer for the entry. If the forwarding entry isfound but the outgoing port list does not include the receiving port, the proxy addsthe port to the outgoing port list as a dynamic member port and starts an agingtimer for it. If no forwarding entry is found, the proxy creates the entry, adds thereceiving port to the outgoing port list as a dynamic member port and starts anaging timer for the port, and then, sends a report to the group out all router ports.LeaveIn response to an IGMP leave message for a multicast group, the proxy sends agroup-specific query out the receiving port. After making sure that no memberport is contained in the forwarding entry for the multicast group, the proxy sends aleave message to the group out all router ports.Protocols and StandardsIGMP snooping is documented in:z RFC 4541: Considerations for Internet Group Management Protocol (IGMP) and Multicast ListenerDiscovery (MLD) Snooping SwitchesIGMP Snooping Configuration Task ListComplete these tasks to configure IGMP snooping:Task RemarksEnabling IGMP Snooping RequiredConfiguring Basic Functionsof IGMP Snooping Configuring the Version of IGMP Snooping OptionalConfiguring Aging Timers for Dynamic Ports OptionalConfiguring Static Ports OptionalConfiguring Simulated Joining OptionalConfiguring IGMP SnoopingPort FunctionsConfiguring Fast Leave Processing OptionalEnabling IGMP Snooping Querier OptionalConfiguring IGMP Queries and Responses OptionalConfiguring IGMP SnoopingQuerierConfiguring Source IP Address of IGMP Queries OptionalConfiguring IGMP Snooping Enabling IGMP Snooping Proxying Optional
