Best asking in the network forum.
I'm stuck on the same issue as well, I've done the same as you. Is your network anything different ? All connected via LAN and not using any Homeplugs? Have you tried disabling any firewalls?
I assume you've got things sorted like static IP address and etc?
If all fails you can get Teamviewer installed and create a quick account, thats how I've done it for me so far. Cannot get RDS working for the live of me.
What's your network mask? Your WHS looks like its outside the typical Class C you would find on most home networks.
What's your routers IP address? If it's something like 192.168.1.1, then it won't be able to communicate with the server 192.168.10.8 with that subnet mask. You would need to put it on the 192.168.1.x range
