3Com 4210 PWR Configuration Manual page 200

198 C 16: IGMP S
HAPTER
Work Mechanism of
IGMP Snooping
C
NOOPING ONFIGURATION
Figure 63 IGMP Snooping related ports
Ports involved in IGMP Snooping, as shown in Figure 63, are described as follows:
Router port: A router port is a port on the Layer 3 multicast device (DR or IGMP
■
querier) side of the Ethernet switch. In Figure 63, Ethernet 1/0/1 of Switch A
and Ethernet 1/0/1 of Switch B are router ports. A switch registers all its local
router ports in its router port list.
Member port: A member port is a port on the multicast group member side of
■
the Ethernet switch. In Figure 63, Ethernet 1/0/2 and Ethernet 1/0/3 of Switch
A and Ethernet 1/0/2 of Switch B are member ports. The switch records all
member ports on the local device in the IGMP Snooping forwarding table.
Port aging timers in IGMP Snooping and related messages and actions
Port aging timers in IGMP Snooping and related messages and actions
Table 144
Timer Description
Router port For each router port, the
aging timer switch sets a timer
initialized to the aging time
of the route port
Member port When a port joins a
aging timer multicast group, the switch
sets a timer for the port,
which is initialized to the
member port aging time
A switch running IGMP Snooping performs different actions when it receives
different IGMP messages, as follows:
When receiving a general query
The IGMP querier periodically sends IGMP general queries to all hosts and routers
on the local subnet to find out whether active multicast group members exist on
the subnet.
Message before Action after
expiry expiry
IGMP general query or The switch removes
PIM hello this port from its
router port list
IGMP membership The switch removes
report this port from the
multicast group
forwarding table