13
Figure 11
IGMP snooping related ports
The following describes the ports involved in IGMP snooping:
•
Router port
—Layer 3 multicast device-side port. Layer 3 multicast devices include designated
routers (DRs) and IGMP queriers. In
, Ethernet 1/0/1 of Switch A and Ethernet 1/0/1 of
Switch B are router ports. The switch registers all its router ports in its router port list.
Do not confuse the "router port" in IGMP snooping with the "routed interface" commonly known as
the "Layer 3 interface." The router port in IGMP snooping is the Layer 2 interface.
•
Member port
—Multicast receiver-side port. In
, 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 registers all its member
ports in its IGMP snooping forwarding table.
Unless otherwise specified, router ports and member ports in this document include both static and
dynamic router ports and member ports.
NOTE:
An IGMP-snooping-enabled switch deems that all its ports on which IGMP general queries with the source
IP address other than 0.0.0.0 or that receive PIM hello messages are received are dynamic router ports.
Aging timers for dynamic ports in IGMP snooping and related messages and actions
Timer Description
Message before expiry
Action after expiry
Dynamic router port
aging timer
For each dynamic router
port, the switch starts an
aging timer. When the
timer expires, the
dynamic router port ages
out.
IGMP general query of
which the source address
is not 0.0.0.0 or PIM
hello.
The switch removes this
port from its router port
list.
