OpenWRT: Multcast Forwarding
From OnnoCenterWiki
Add the following in /etc/rc.local
echo "0" > /sys/devices/virtual/net/br-lan/bridge/multicast_snooping
Replace br-lan with your actual bridge interface, sometimes also called br0.
This will forward all multicast packets to all ports on your bridge, making igmpproxy or udpxy unnecessary. In large networks, this may not be desirable.