20is receiving or expecting to receive multicast data for the multicast group. The switch restarts theaging timer for the port.• If the port receives no IGMP report in response to the group-specific query before its aging timerexpires, it indicates that no hosts attached to the port are still listening to that group address. Theswitch removes the port from the forwarding entry for the multicast group when the aging timerexpires.IGMP snooping proxyingYou can configure the IGMP snooping proxying function on an edge device to reduce the number ofIGMP reports and leave messages sent to its upstream device. The device configured with IGMPsnooping proxying is called an IGMP snooping proxy. It is a host from the perspective of its upstreamdevice.Even though an IGMP snooping proxy is a host from the perspective of its upstream device, the IGMPmembership report suppression mechanism for hosts does not take effect on it. For more informationabout the IGMP report suppression mechanism for hosts, see "Configuring IGMP (available only on theS5500-EI)."Figure 13 Network diagramAs shown in Figure 13, Switch A works as an IGMP snooping proxy. As a host from the perspective of thequerier Router A, Switch A represents its attached hosts to send membership reports and leave messagesto Router A.Table 6 IGMP message processing on an IGMP snooping proxyIGMP message ActionsGeneral queryWhen receiving an IGMP general query, the proxy forwards it to allports but the receiving port. In addition, the proxy generates a reportaccording to the group memberships it maintains and sends the reportout of all router ports.Host AReceiverHost BHost CReceiverIGMP QuerierRouter AProxy & QuerierSwitch AQuery from Router AReport from Switch AQuery from Switch AReport from HostIP network
