14
Figure 12 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
, GigabitEthernet 1/0/1 of Switch A and
GigabitEthernet 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
, GigabitEthernet 1/0/2 and
GigabitEthernet 1/0/3 of Switch A and GigabitEthernet 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 that receive IGMP general queries with
the source IP address other than 0.0.0.0 or that receive PIM hello messages are dynamic router
ports. For more information about PIM hello messages, see "
."
Aging timers for dynamic ports in IGMP snooping and related messages and actions
Timer Description
Expected message
before expiration
Action after
expiration
Dynamic router port
aging timer
When a port receives an
expected message, the
switch starts an aging
timer for the port. 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.
Dynamic member port
aging timer
When a port dynamically
joins a multicast group,
the switch starts an
aging timer for the port.
When the timer expires,
the dynamic member
IGMP membership
report.
The switch removes this
port from the IGMP
snooping forwarding
table.
