Security enhancement for IGMP
A security enhancement was made to IGMPv2 to comply with the following recommendation of RFC 2236: “Ignore the Report if you cannot identify the source address of the packet as belonging to a subnet assigned to the interface on which the packet was received.”
NOTE
When used in applications such as IP-TV (or any multicast application in general), the administrator should ensure that the set-top box (or multicast client) is configured on the same subnet as the v.e. configured on the device. This is typically the case but is emphasized here to ensure correct operation. Without this configuration, IGMP messages received by the device are ignored, which causes an interruption in any multicast traffic directed towards the set-top box (multicast client).