Softether is a software VPN capable of L2TP/IPSEC functionality, this is a software VPN that can be installed on almost any OS.
It is compatible with almost every platform including mobile phones, it can also function as an OpenVPN server,
if your trying to secure network traffic or simply want to join multiple sites to create centralized resources; this VPN software could be your final solution!
Installation is probably 6/10 on the difficulty scale, so not to hard if you can follow coded instructions. This VPN server can be managed from the command line or from a Windows based GUI Application.