We are installing a SMS gateway with Kannel, on a CentOs 6.5 server, which is supposed to connect via SMPP to our local operators. Kannel is working fine and no probleme there. Now 2 operators are asking to connect via a VPN for obvious security reasons; actually they asked for or VPN details so they can connect to it... Now, I am looking for a free VPN that I can setup and configure on our server... I saw Open VPN that I already started configuring, no issue... But just saw on Wikipedia (http://en.wikipedia.org/wiki/OpenVPN#Platforms) that OpenVPN is not compatible with other VPN packages. Now my question is: 1- I am absolutely new to VPN technologies. Is OpenVPN a good choice in my situation? 2- If I configure OpenVPN on my server, will it be possible to any client to connect to my server? 3- Anyone have any advice for me? Thank you for this great community.