I have a Linux router (Ubuntu). It is working well with unicast but with multicast routing/forwarding I have some trouble.

The problem is that my hosts do not send igmp/mld messages thus the router does not learn that there are interested parties on a link.

How can I manually configure the forwarding. So that multicasts coming to eth0 are forwarded out eth1.

I was trying to make it work with the following command: route add -net netmask eth0

But this seems only to be used for outgoing traffic.

I also tried out smcroute, but this daemon does not work on my Ubuntu.

Is it possible with iptables to do the forwarding? Or with this route add command?



A little late on this one, but here is a pretty solid guide http://troglobit.github.io/multicast-howto.html. At the end he mentions:

iptables -t mangle -A OUTPUT -d <group> -j TTL --ttl-set <num>

But my understanding is that you would want your network switches to handle the igmp querying/forwarding which your router would then use.

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