Figure 228 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 228, 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 228, GigabitEthernet 1/0/2 and GigabitEthernet 1/0/3 of Switch A and GigabitEthernet 1/0/2 of Switch B are member ports. A switch records all its 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

Action after the timer

the timer expires

expires

 

 

Dynamic router port aging timer

When a port receives an IGMP general query with the source address other than

0.0.0.0or PIM hello message, the switch starts or resets an aging timer for the port. 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.

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