H3C S9500 Series Operation Manual

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H3C S9500 Series Operation Manual Manual pdf 6 page image

Operation Manual – IGMP SnoopingH3C S9500 Series Routing Switches Chapter 1 IGMP Snooping Configuration1-41.1.3 Work Mechanism of IGMP SnoopingCaution:Only dynamic ports can be automatically added or deleted by the system. Static portscan be added or deleted only through the corresponding configurations.A switch running IGMP Snooping performs different actions when it receives differentIGMP messages, as follows:I. When receiving a general queryThe IGMP querier periodically sends IGMP general queries to all hosts and routers onthe local subnet (224.0.0.1) to find out whether active multicast group members existon the subnet.Upon receiving an IGMP general query, the switch forwards it through all ports in theVLAN except the receiving port, and performs the following to the port on which itreceived the query message:z If the port is a dynamic router port existing in the router port list, the switch resetsthe aging timer for this dynamic router port.z If the port is not a dynamic router port existing in its router port list, the switch addsit into the router port list and sets an aging timer for this dynamic router port.II. When receiving a membership reportA host sends an IGMP report to the IGMP querier in the following circumstances:z Upon receiving an IGMP query, a multicast group member host responds with anIGMP report.z When intended to join a multicast group, a host sends an IGMP report to the IGMPquerier to announce that it is interested in the multicast information addressed tothat group.Upon receiving an IGMP report, the switch forwards it through all the router ports in theVLAN, resolves the address of the multicast group the host is interested in, andperforms the following to the receiving port:z If no forwarding table entry exists for the reported group, the switch creates anentry, adds the port as a dynamic member port into the outgoing port list, andstarts a member port aging timer for that port.