I rebuilt my homelab using the instructions in the link below and the end result (3 servers behind one router...not quite his awesome setup) was much better than my previously built lab:

How to emulate a network using VirtualBox | Open-Source Routing and Network Simulation

Its actually a suitable reference to create a dev/test environment on your production network. I highly recommend trying it at least once, especially if you're interesting in configuring Linux as a router. Back to studying..