You will need a sound interface on the second machine with SPDIF or AES and an ASIO driver and a VST System Link driver (this could be another instance of Cubase, Nuendo, or any app with VST System Link). Now, connect the digital out of first machine to digital in of second machine. Then, connect digital out of second machine to digital in of first machine. You can do this with as many digital in/out pairs that you want to use. Just like any digital interface you will need to set the clocks in synch on both machines and set one as master, one as slave. Make sure sample rates are the same on both applications (Cubase on machine one, whatever you have on machine two). Check your TotalMix settings, you don't want any feedback loops. Activate VST System Link on both machine's apps. You can now stream audio back and forth (you will need to set up some busses) and send and receive timecode and transport signals and MIDI.
Good luck. I have done this a few times. It is really not that hard, just pay attention to the I/O's and settings. If you are successful, congratulations! You will have a mondo, sample-accurate, virtual RAID for tracking (or perhaps a full blown 24-bit Halion Orchestra offloaded on one machine and a 6 piece metal band on the other).
Marty Laye - Owner/Engineer
mobilatracks.com