You can find the IGMPProxy Settings at Services → IGMPProxy.
The IGMPProxy is used to propagate multicasts across L2s.
Before you can use the IGMPProxy it has to be installed. You can install it at System → Addons.
On the page the IGMPProxy can be enabled or disabled.
Interface sets the interface. This interface can not be used as Downstream interface.
Threshold for the TTL of the multicast to avoid looping. Default value is 1.
You can add multiple Networks, each with an IP Address and Netmask.
You can add multiple Downstreams, each with an Interface and Threshold.
After saving a Downstream Interface you can optionally set Networks to specify who is allowed to communicate via the IGMP proxy.
It’s not possible to use the Upstream interface as Downstream interface.