Openvpn

Install openvpn server in ubuntu 16.04
https://www.digitalocean.com/community/tutorials/how-to-set-up-an-openvpn-server-on-ubuntu-16-04
Reference - https://www.digitalocean.com/community/tutorials/how-to-setup-and-configure-an-openvpn-server-on-centos-6
Reference - https://www.digitalocean.com/community/tutorials/how-to-set-up-an-openvpn-server-on-ubuntu-14-04
http://mtehrani30.blogspot.co.uk/2008/03/openvpn-clientss-static-ip.html