Hi

I'm having an issue where the 2830n still reports to the WAN that it is a member of a multicast group, despite the fact that no downstream interfaces are requesting the traffic.

In more detail:

Normally, if a device on a downstream interface (i.e. one of the LAN ports) such as a YouView set-top box wants a multicast stream (such as an IPTV channel), it sends a message to the Draytek to join that multicast group. The igmp proxy in the Draytek then sends a join message upstream via the WAN to join that stream, and the traffic starts to come to the WAN which the Draytek then passes onto the appropriate LAN port.

If you finish watching the TV channel, the set-top box sends a leave message to the Draytek. What should happen then, if no-one else is watching the channel, is that the Draytek itself leaves the multicast group, notifies the upstream network and the traffic stops coming to the WAN.

However, this doesn't happen. If you stop watching the TV channel, the set top box tells the Draytek but, for whatever reason, the Draytek continues to report upstream that it is still a member of the multicast group and the traffic associated with the TV channel keeps being sent to the Draytek, which then just dumps it (because no downstream interface wants it anymore). You can see this on the lights as the WAN is flashing like crazy, but the LAN ports aren't. Basically that means that once you've watched a TV channel, the router downloads the 2.5MB/sec associated with that channel forever more. The only way to stop it is to reboot the router.

You can also see it from the following screenshot:



The 233.51.229.113 multicast group is an IPTV channel, responsible for 2.5MB/sec of incoming traffic via the WAN. However, you can see that none of the LAN ports are requesting that traffic. Why is the 2830n still reporting that it's a member of the group to the WAN despite the fact that no downstream LANs are requesting the traffic?