...Small (~25 KB), with an equally small and readable code base. No external dependencies. Works out of the box. No lousy documentation to read. No configuration file. No post-configuration. Run a single-line command on the server, a similar one on the client and you're done. No firewall and routing rules to manually mess with. Doesn't leak between reconnects if the network doesn't change. Blocks IPv6 on the client to prevent IPv6 leaks. Works on Linux (kernel >= 3.17), macOS and OpenBSD, as well as DragonFly BSD, FreeBSD and NetBSD in client and point-to-point modes. ...
OpenVPN is a robust and highly flexible tunneling application that uses all of the encryption, authentication, and certification features of the OpenSSL library to securely tunnel IP networks over a single TCP/UDP port.
Discussion forums and project wiki can be found here:
https://forums.openvpn.net/
http://community.openvpn.net/openvpn