When my TV recorder receives multicast (IPTV), my other box receives the same stream, too. I use a TP-Link VR200v with a 4 port switch with VLAN disabled.
Here they say, that there is a bug in the "option igmp_snooping 1".
How can I fix it?
Is there a way for iptables to block multicast traffic to certain switch ports?
In order to get IGMP snooping or ipv6 MLD snooping on a piece of hardware you probably want to use a dedicated managed hardware switch that specifically mentions it in the feature list.
The hardware chips in typical home / consumer routers may or may not support IGMP snooping, and probably none of them support MLD snooping. When you enable igmp_snooping on the linux bridge it doesn't change anything on the hardware switch chip. so anything that gets injected into the switch by the CPU gets broadcast unless the switch supports snooping and the snooping is turned on somehow (swconfig? DSA? I'm not sure).