QTECH
Software Configuration Manual
10-132
10.4.2
Basic Concepts in IGMP Snooping
10.4.2.1
IGMP Snooping related ports
As shown in Figure 2, Router A connects to the multicast source, IGMP Snooping runs on Switch A and
Switch B, Host A and Host C are receiver hosts (namely, multicast group members).
Figure 2 IGMP Snooping related ports
Ports involved in IGMP Snooping, as shown in Figure 2, are described as follows :
·
Router port : A router port is a port on the Ethernet switch that leads switch towards the Layer 3
multicast device (DR or IGMP querier). In the figure, Ethernet 1/0 of Switch A and Ethernet 1/0 of
Switch B are router ports. The switch registers all its local router ports (including static and dynamic
router ports) in its router port list.
·
Member port : A member port is a port on the Ethernet switch that leads switch towards multicast
group members. In the figure, Ethernet 0/0/1/1 and Ethernet 1/2 of Switch A and Ethernet 0/0/1/1 of
Switch B are member ports. The switch registers all the member ports (including static and dynamic
member ports) on the local device in its IGMP Snooping forwarding table.
&
Note :
l
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.
l
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.
10.4.2.2
Port aging timers in IGMP Snooping and related messages and
actions
Table 1
Port aging timers in IGMP Snooping and related messages and actions
Timer
Description
Message before expiry
Action after expiry
