H3C Technologies H3C WX6000 Series Access Controllers - Manual (Page 175)

24-3
A and Ethernet 1/2 of Switch B are member ports. A switch registers all its member ports in the IGMP
snooping forwarding table.
Whenever mentioned in this document, a router port is a port on the switch that leads the switch to
a Layer 3 multicast device, rather than a port on a router.
Unless otherwise specified, router ports and member ports mentioned in this document consist of
dynamic and static ports.
An IGMP-snooping-enabled switch deems that all its ports on which IGMP general queries with the
source address other than 0.0.0.0 or PIM hello messages are received to be router ports.
Work Mechanism of IGMP Snooping
A switch running IGMP snooping performs different actions when it receives different IGMP messages,
as follows:
You can add or delete only dynamic ports rather than static ports.
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 any 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:
The switch resets the aging timer for the receiving port if the port is in the router port list;
The switch adds the receiving port to the router port list if it is not in the list and starts the aging
timer for the port.
When receiving a membership report
A host sends an IGMP membership report to the IGMP querier in the following circumstances:
Upon receiving an IGMP query, a multicast group member host responds with an IGMP report;
When intended to join a multicast group, a host sends an IGMP report to the querier to announce
its interest 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:
If no forwarding table entry exists for the reported group, the switch creates an entry, adds the port
as a member port to the outgoing port list, and starts a member port aging timer for that port.