H3C S5810 Series, Руководство по эксплуатации

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When receiving a general query
The IGMP querier periodically sends IGMP general queries to all hosts and routers (224.0.0.1) on the
local subnet to find out whether active multicast group members exist on the subnet.
Upon receiving an IGMP general query, the switch forwards it through all ports in the VLAN except the
receiving port and performs the following to the receiving port:
z
If the receiving port is a dynamic router port existing in its router port list, the switch resets the aging
timer of this dynamic router port.
z
If the receiving port is not a dynamic router port existing in its router port list, the switch adds it into
its router port list and sets an aging timer for this dynamic router port.
When receiving a membership report
A 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 an IGMP report.
z
When intended to join a multicast group, a host sends an IGMP report to the IGMP querier to
announce that it is interested in the multicast information addressed to that group.
Upon receiving an IGMP report, the switch forwards it through all the router ports in the VLAN, resolves
the address of the reported multicast group, and performs the following:
z
If no forwarding table entry exists for the reported group, the switch creates an entry, adds the port
as a dynamic member port to the outgoing port list, and starts a member port aging timer for that
port.
z
If a forwarding table entry exists for the reported group, but the port is not included in the outgoing
port list for that group, the switch adds the port as a dynamic member port to the outgoing port list,
and starts an aging timer for that port.
z
If a forwarding table entry exists for the reported group and the port is included in the outgoing port
list, which means that this port is already a dynamic member port, the switch resets the aging timer
for that port.
A switch does not forward an IGMP report through a non-router port. This is because if the switch
forwards a report message through a member port, all the attached hosts listening to the reported
multicast address will suppress their own reports upon receiving this report according to the IGMP
report suppression mechanism on them, and this will prevent the switch from knowing whether the
reported multicast group still has active members attached to that port.
When receiving a leave message
When an IGMPv1 host leaves a multicast group, the host does not send an IGMP leave message, so
the switch cannot know immediately that the host has left the multicast group. However, as the host
stops sending IGMP reports as soon as it leaves a multicast group, the switch deletes the forwarding
entry for the dynamic member port corresponding to the host from the forwarding table when its aging
timer expires.