tinc

tinc is a free and open-source Virtual Private Network daemon capable of creating a VPN between hosts on the web by taking advantage of tunneling and encryption. It can compress traffic using zlib and LZO as well as encrypt it using LibreSSL and OpenSSL so that it doesn't get mixed up with sequence numbers and message authentication codes.
Automatic full mesh routing is supported so that VPN traffic is always sent to the destination directly when this is possible, without the need of resorting to multiple hops. Peers can communicate directly thanks to NAT traversal, provided that there's at least one node in the VPN which permits incoming connections on a public IP address, whether it's static or dynamic.
To be able to add more nodes to the VPN, it's only necessary to create and add other configuration files. This means that you don't have to start new daemons or customize settings for new devices or network adapters. Multiple Ethernet segments can be bridged to work as one, thus making it possible to launch games and apps that typically work only in a local network over the web.
In addition to Windows, tinc can be installed on FreeBSD, Linux, OpenBSD, Mac OS X, NetBSD, and Solaris. IPv6 networks are supported. User documentation is available on the developer's website.

System requirements