Network Load Balancing not working with UDP traffic (Server 2012)

Hi all,

I manage an application that receives traffic from mobile devices on cellular networks. The traffic is UDP. I have set up two x Server 2012 VMs to form part of a NLB cluster. Each server has a second NIC dedicated to NLB. The traffic is simply NATed from our firewalls to the virtual IP. When looking at the traffic using a packet sniffer, I can see the traffic being routed correctly to the virtual IP, but the problem is that the return traffic is sent from the IP address on the actual NIC. My application does not like the fact that the return traffic is coming from a different source IP. Is there any way to force the return traffic to also come from the virtual IP address?

Thanks!