@sega said in FOG Multicast on different VLANs:
Is there something that I can look up, to see where the problem is?
Well your router supporting PIM is a good sign. Some routers have a service called igmp proxy or igmp relay, or even igmp snooping (you will find this more on switches, but check). This service typically has a number of interfaces to listen on and then a master interface where your multicast source lives. Its job is to relay the multicast requests to the proper interface.
PIM has two modes sparse and dense, that may be just for switches, I don’t remember. Sparse mode only sends the multicast traffic to the subscriber’s port, where dense just blasts out the muticast to all ports. You want sparse mode if possible, that way only the ports with a multcast receiver will see the traffic and not flood your network.

