Technology has reached a level now that you can build a very nice router. All it takes is printing out (or save to PDF) this page and following the step-by-step instructions. You have to get the hardware, but as the article shows, you have a couple of options. The step-by-step guide is a good intro to this process and would outfit you with good hands-on experience with routing technology. Understand, that the core information shared in this article does scale to business class scenarios. With few tweaks and more reading, you can expand the example to include building a cable modem and a WiFi router.