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Figure 241 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 and IGMP queriers. In Figure 241 , GigabitEthernet 1/0/1 of Switch A and GigabitEthernet
1/0/1 of Switch B are router ports. A switch records all its local 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 Figure 241 , GigabitEthernet 1/0/2 and
GigabitEthernet 1/0/3 of Switch A and GigabitEthernet1/0/2 of Switch B are member ports. A
switch records all local member ports in the IGMP snooping forwarding table.
Unless otherwise specified, router ports and member ports in this document include both dynamic and
static ports.
NOTE:
When IGMP snooping is enabled, all ports that receive PIM hello messages or IGMP general queries with
the source addresses other than 0.0.0.0 are considered dynamic router ports.
Aging timers for dynamic ports in IGMP snooping
Timer Description
Message received
before the timer
expires
Action after the timer
expires
Dynamic router port
aging timer
For each dynamic router port,
the switch sets an aging timer.
When the timer expires, the
dynamic router port ages out.
IGMP general query with
the source address other
than 0.0.0.0 or PIM hello
message.
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 sets an aging timer for
the port. When the timer
expires, the dynamic member
port ages out.
IGMP membership
report.
The switch removes this
port from the IGMP
snooping forwarding
table.