IGMP (Internet Group Management Protocol) snooping and IGMP treat the VLAN (Virtual LAN) as an interface. Only control packets with a source address belonging to the IP networks configured on that interface are accepted.
IGMP accepts membership information that originates from hosts in both the primary and secondary subnets. The following describes the changes in behavior of IGMP in an IP multinetting environment:
A Layer 3 VLAN always uses the primary IP address as the source address to send out an IGMP query, and querier election is based on the primary IP address of interface. Because the RFC dictates that there is only one querier per physical segment, the querier may be attached to any of configured IP interfaces, including secondary interfaces, although this is not a recommended configuration.
For a static IGMP group, the membership report is also sent out using the primary IP address.
For local multicast groups such as 224.0.0.X, the membership report is sent out using the first IP address configured on the interface, which is the primary IP address in ExtremeXOS.
The source IP address check is disabled for any IGMP control packets (such as IGMP query and IGMP membership report). Source IP address checking for IGMP control packet is disabled for all VLANs, not just the multinetted VLANs.
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