Routing is normally performed by a router, (the clue's in the name), you can use a PC as a router and even run multiple subnets, but you will need at least one Network Interface for each Subnet, plus specialist software or a full knowledge of the command line command structure for networking.
I've not seen any home user router that can perform proper sub-neting, which you normally control using a managed switch, the word router is normally reserved for devices in the home or those supporting Wireless.
First place to look would probably be someone like Cisco they have a library of information, a lot of which is available as PDF
The router has to be programmed to allow subnetting plus have multiple independent interfaces. Home routers don't usually have that and I actually don't know of any that do since most homes don't do this. You will have to get an enterprise sized router from for example cisco. Perhaps this should be merged with his previous thread. http://www.vistax64.com/network-sha...ress-different-subnet-still-has-internet.html