I need to route IGMP/Multicast traffic across two networks. I have a Linux box with two NICs, one public, one private. Need devices on the private network to flow to public. I'm pretty certain I have iptables set up right, been trying to do this with IGMPProxy. It doesn't work on PCs on provate, but from the Linux server I can ping 224.0.0.1.
you can route multicast traffic on Linux using mrouted. It's quite old but still working... :-)
IGMP works only in a link-local scope and you should not try to route it with iptables.
You can setup some IGMP routing daemon like the one provided by Xorp.org or you can discard the IGMP information (if your setup is static) and use use smcroute to manipulate the kernel multicast routing table.