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I have an application that needs to send UDP multicast data "from" either one or two physical NICs on a single Windows Server 2008 machine. In the two NIC configuration, every datagram needs to be sent through both physical NICs. Each NIC is on a different subnet, and so the source address of the redundant datagrams needs to correspond to the actual physical NIC.

While I could obviously just send the data once or twice within the application, I would prefer the application to be agnostic of the network configuration.

Is there anything out there that could address this? It doesn't particularly matter if the answer is hardware, drivers, or OS configuration.

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I'm assuming each NIC is on a different subnet? – gravyface Sep 10 '10 at 14:20
Yes, each NIC is on a different subnet. – Patrick Johnmeyer Sep 10 '10 at 14:29
ok so you know that you'd need to change the src address for each datagram, right? I can't think of how this would work without either sending each packet twice in your application (or having a proxy do it). – gravyface Sep 10 '10 at 15:43
Yes, you are describing precisely what I need. I'll update the question with your clarifications. – Patrick Johnmeyer Sep 10 '10 at 15:58

I think you're looking for something called NIC Teaming. (or bonding.) The official standard is LACP. Unfortunately, that's not supported on Windows. Works great in Linux, though. ;-)

On Windows, it is still possible. However, it is vendor implemented via their own driver package. I know Intel and HP have products that support this. So check your options in the NIC driver details page.

It should be noted that this does require some support from the switch itself. Most modern ones will have that ability, it will just take some configuration.

--Christopher Karel

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My understanding of LACP is that it offers redundancy in a failover fashion, and/or increased bandwidth by sending portions of the data out of two NICs. What I am looking for is sending the same data out of both NICs. Updating the question to clarify. – Patrick Johnmeyer Sep 10 '10 at 14:10

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