Describes the IGMP snooping function on APIC, including IGMPv1 and IGMPv2 support and the fast leave feature.
The APIC IGMP snooping function is a multicast management mechanism that
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supports both IGMPv1 and IGMPv2 with membership report suppression
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enables fast leave feature configuration in IGMPv2 environments, and
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manages multicast data forwarding based on IGMP messages.
Membership report suppression and fast leave behavior
Both IGMPv1 and IGMPv2 support membership report suppression, which means that if two hosts on the same subnet want to receive multicast data for the same group, the host that receives a member report from the other host suppresses sending its report. Membership report suppression occurs for hosts that share a port.
If no more than one host is attached to each switch port, you can configure the fast leave feature in IGMPv2. The fast leave feature does not send last member query messages to hosts. As soon as APIC receives an IGMP leave message, the software stops forwarding multicast data to that port.
IGMPv1 does not provide an explicit IGMP leave message, so the APIC IGMP snooping function must rely on the membership message timeout to indicate that no hosts remain that want to receive multicast data for a particular group.
The IGMP snooping function ignores the configuration of the last member query interval when you enable the fast leave feature because it does not check for remaining hosts.