How to set up a compute node only application network

I am setting up a compute cluster using HPC Server 2008 R2 cluster manager and have my compute nodes isolated on a private network, to which the head node is also connected, but I also have a high-speed application network running between my compute nodes only. How do I configure the networking for the cluster? I can't use topology 3, as my head node only has 2 network adapters.

Thanks