This read-write attribute controls whether IGMP multicast traffic is forwarded upstream from the ComPort, and it overrides any other multicast filtering specifically for IGMP packets; default is enable. Because IGMP join/leave messages are what let a subscriber's set-top box or media device signal interest in a multicast video stream, disabling this would break multicast services even if other multicast filters look correctly configured. For example, if a subscriber can't join any multicast IPTV channel, checking that stuEtherIgmpEnable is still set to enable would be an early troubleshooting step.