Multicast management (IGMP Snooping)

Hi, guys!

I have RB750.
In Ether1 I have recieved multicast traffic from switch with IGMP Snooping.
In Ether2 and Ether3 I have connected IP STBs. Ether1,2,3 is Brigde ports.
When STB/Ether2 joing multicast group, then STB/Ether3 recieve
the same traffic. How to manage multicast in MT OS? Does MT have IGMP Snooping or some similar function?

Thanks!