15
•
If a match is found but the receiving port is not in the forwarding entry, the Layer 2 device
discards the IGMP leave message.
•
If a match is found and the receiving port is in the forwarding entry, the Layer 2 device forwards
the leave message to all router ports in the VLAN. The Layer 2 device does not immediately
remove the port from the forwarding entry for that group. Instead, it adjusts the aging timer for
the port.
After receiving the IGMP leave message, the IGMP querier resolves the multicast group address in
the message. Then, it sends an IGMP group-specific query to the multicast group through the port
that received the leave message.
After receiving the IGMP group-specific query, the Layer 2 device forwards the query through all its
router ports in the VLAN and all member ports of the multicast group. Then, it waits for the
responding IGMP reports from the directly connected receivers. For the dynamic member port that
received the leave message, the Layer 2 device also performs one of the following actions:
•
If the port receives an IGMP report before the aging timer expires, the Layer 2 device restarts
the aging timer for the port.
•
If the port does not receive an IGMP report when the aging timer expires, the Layer 2 device
removes the port from the forwarding entry for the multicast group.
Protocols and standards
RFC 4541,
Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener
Discovery (MLD) Snooping Switches
IGMP snooping configuration task list
Tasks at a glance
Configuring basic IGMP snooping features
•
(Required.)
•
(Optional.)
Specifying an IGMP snooping version
•
(Optional.)
Setting the maximum number of IGMP snooping forwarding entries
Configuring IGMP snooping port features
•
(Optional.)
Setting aging timers for dynamic ports
•
(Optional.)
•
(Optional.)
Configuring a port as a simulated member host
•
(Optional.)
Enabling fast-leave processing
•
(Optional.)
Disabling a port from becoming a dynamic router port
Configuring the IGMP snooping querier
:
•
(Optional.)
Enabling the IGMP snooping querier
•
(Optional.)
Configuring parameters for IGMP queries and responses
Configuring parameters for IGMP messages
:
•
(Optional.)
Configuring source IP addresses for IGMP messages
•
(Optional.)
Setting the 802.1p priority for IGMP messages