How to Setup a L2TP VPN Server on OS X

http://jonsview.com/how-to-setup-os-x-10-9-as-a-l2tp-vpn-server-without-apples-server-app

This is a fast guide on configuring OS X to act as an L2TP VPN Server. This can be accomplished with Apple’s Server App, but if you don’t mind running a few Terminal commands and adding a couple configuration files manually, you can save yourself $20 and go out to eat instead.