Protocols And Standards - HP FlexNetwork 7500 Series Configuration Manual

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If no match is found, the Layer 2 device discards the IGMP leave message.
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If a match is found but the receiving port is not an outgoing interface in the forwarding entry, the
Layer 2 device discards the IGMP leave message.
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If a match is found and the receiving port is not the only outgoing interface in the forwarding
entry, the Layer 2 device performs the following actions:
Discards the IGMP leave message.
Sends an IGMP group-specific query to identify whether the group has active receivers
attached to the receiving port.
Sets the aging timer for the receiving port to twice the IGMP last member query interval.
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If a match is found and the receiving port is the only outgoing interface in the forwarding entry,
the Layer 2 device performs the following actions:
Forwards the IGMP leave message to all router ports in the VLAN.
Sends an IGMP group-specific query to identify whether the group has active receivers
attached to the receiving port.
Sets the aging timer for the receiving port to twice the IGMP last member query interval.
After receiving the IGMP leave message on a port, 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 receiving port.
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 report from the directly connected hosts. For the dynamic member port that
received the leave message, the Layer 2 device also performs one of the following actions:
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If the port receives an IGMP report before the aging timer expires, the Layer 2 device resets the
aging timer.
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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
General configuration restrictions and guidelines
When you configure IGMP snooping, follow these restrictions and guidelines:
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For a VLAN configured with IGMP snooping, if you change the VPN instance bound to the
VLAN interface, Layer 2 multicast traffic for the VLAN is interrupted. In this case, you must
execute the reset igmp-snooping group command so that new IGMP snooping forwarding
entries can be created.
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For IGMP reports received from secondary VLANs, the relevant IGMP snooping forwarding
entries are maintained by the primary VLAN. Therefore, you need to configure IGMP snooping
only for the primary VLAN. The IGMP snooping configuration made for secondary VLANs does
not take effect. For more information about primary VLANs and secondary VLANs, see Layer
2—LAN Switching Configuration Guide.
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The IGMP snooping configurations made on Layer 2 aggregate interfaces do not interfere with
the configurations made on member ports. In addition, the configurations made on Layer 2
aggregate interfaces do not take part in aggregation calculations. The configuration made on a
member port of the aggregate group takes effect after the port leaves the aggregate group.
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