Artnet DMX / How to specify a network interface?

I am working on a patch that makes use of a the Artnet DMX sender. My computer has several network cards, one of which I have set to the IP/DNS settings required by Artnet ( / If I disable all network interfaces apart from the one card set with the correct details, the DMX output works. The moment I enable other network interface cards (ie. to get internet access), the DMX output fails.
I guess there must be a way to force the VVVV patch (or even specifically the DMX sender) to use a specific network card?!? How do I do that?
Thank you!

IP basically uses the network mask to determine which network card is used for sending. thats the reason why there is no pin to force to use a specific card in vvvv. so if you set configure the card to ( /, everything send to 2.x.x.x will go to this card. everything not matching the network adress will be routed to the default gateway (so it makes sense not to set a default gateway in the artnet subnet)

perhaps your internet provider is also using a 2.x.x.x network?

Oschatz, thank you for the reply.

I have checked all network settings on my computer (windows vista x64 on Mac Pro tower) an am certain that there are no references to 2.x.x.x or on any other network interface/connection beyond the LAN port I have set up specifically for the artNet connection.

Is there anything else I should try?