Ubuntu based VPN server behind NAT router?

Question

I have a small intranet- and file-server inside our company, which can only be reached from inside our own network. I'd like to be able to reach the intranet and files on the server from outside the network, however I don't really like the idea of completely opening security by forwarding the ports on our NAT-router, so I'd prefer to enable a VPN possibility for this.

So I have a router, which is the DHCP server and has NAT function, and I have an Ubuntu Server with the files and intranet on it. How do I configure these two so that I can make a VPN connection with my network in order to reach the server?

thanks in advance for any answer!

Solution 1

For a PPTP server, forward TCP port 1723, and GRE Protocol (protocol 47).

Configure Ubuntu to be a PPTP VPN server as per: Configure a PPTP VPN Server on Ubuntu Linux

Solution 2

OpenVPN is good solution. You can setup authentication based on username and/or certificate. Also with this setup all remote users will access the server from different network. You can use this to apply special firewall rules or access permisions. The port and protocol which OpenVPN uses are configurable. P.S. I'm not saying that PPTPD won't do the job. I just have more experience with OpenVPN.

Solution 3

Port forward 1194/udp to the ubuntu and follow this excellent tutorial (don't forget that you can apt-get install openvpn -y on debian/ubuntus).