Thanks for your post, but I'm sorry to say I'm finding this is bit unclear. In topology, you have the master, mediator, and host. The host is the component that actually sends the virtual client's web requests. The host should not be sending any traffic back to the master/mediator until the load test is completed, however...
The only thing I can think of is performance counters -- the load balancing algorithm needs access to the performance counters to work properly, but if that bit fails, there should come an error message.
ANTS Load wasn't designed with having it's topology spread across different networks -- it didn't seem like a practical sceanrio for load testing as the network connection could be a severe bottleneck and get saturated long before the load starts affecting the web server.
But if this is practical for you, you may want to look into setting up a VPN and allowing NETBIOS over TCP so that you can get the performance counter information through:
http://www.red-gate.com/messageboard/vi ... php?t=3659