Yes, there is only one device connected to the "modem", but not clear what you are referring to: "a switch in there".
If by "global IP" you are referring to the public IP address of the "modem" device (visiable to the public internet), that IP address is passed thru to the Windows 8 box which is successfully running Apache and serving web pages.
Yes, I think we are on the same page when you say "global IP of XXX.XXX.XXX.XXX looks like YYY.YYY.YYY.YYY inside". The Apache server & pingable public IP address 108.XXX>XXX.XXX look like 192.XXX.XXX.XXX inside the local network.
The first problem "Bad Request - Invalid Hostname" when accessing the Window 8 public domain with port ":42422" could indeed be a network setup ("modem" configuration) problem. I won't be there to look for a couple of days.
There is potentially a more severe second problem related to origin policy violation when I attempt to access FuseGL's XML output from a web page served by the Apache server by using XMLHttpRequest(). I'm still testing, but the Windows 8 box is currently not accessible.

