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I have a server with multiple NICs on it. Each NIC is plugged into a different, isolated network that is serving multicast traffic. I have a program that listens to the multicast traffic on each of these networks. Right now I have to specify in my program which interface to use as part of the multicast join. This is not a big deal, but is slightly inconvenient.

Is it possible to use routes to influence this process? Suppose I have two multicast groups as follows:

A.  39312 eth1
B. 59328 eth2

Can I add two routes to the routing table such that when I join the multicast group from my code the kernel knows to send group A's join out eth1 and group B's join out eth2? I've been unable to get it to behave the way I want. Adding various routes seems to not affect this process, and the only way I've found to be able to influence which interface is chosen is to specify it in code as part of the multicast_request data structure.

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I would guess that you probably need to look at installing a routing daemon to enable multicast routing and group management. I haven't had an opportunity to really play with it much. I did have to setup Xorp to get some multicast features of a VOIP system to work.

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