Setup Your Own Private Network With OpenVPN

Vultr offers you awesome private network connectivity for servers running at the same location. But sometimes you want two servers in different countries / datacenters to be able to communicate in a private and secure way. This tutorial will show you how to achieve that with the help of OpenVPN. The operating systems used here are Debian and CentOS, just to show you two different configurations. This can be easily adapted for Debian -> Debian, Ubuntu -> FreeBSD and so on.

• Machine 1: Debian, will act as server (Location: NL)
• Machine 2: CentOS, will act as client (Location: FR)

Machine 1

Start on machine 1 by installing OpenVPN:

Then, copy the example configuration and the tool for generating keys, easy-rsa, to /etc/openvpn:

The default values for your keys aren’t exactly safe anymore, to fix this open /etc/openvpn/easy-rsa/2.0/vars with your favorite text editor and modify the following line:

Next, ensure that the values are loaded into your current session, clean up eventually existing keys, and generate your certificate authority:

You will be prompted for information. Make your life easier by supplying information about your server, for example, where it’s located and what the FQDN is/will be. This is useful for when you have to debug problems:

Another necessity is parameters for the Diffie-Hellman key exchange. Those need to be generated too:

Important: The build-dh command is a relatively complex process that can take up to ten minutes, depending on your server’s resources.

To further improve the security of this connection, we will generate a static secret that needs to be distributed amongst all clients:

Now, you can generate the key for the server:

This command will prompt for some information:

The final step is to sign the certificate request that was just generated with the CA’s key:

Copy the necessary keys and certificates into a separate folder:

Now for the configuration, unzip it …

… and open the resulting server.conf with your favorite text editor. The configuration should look similar to this:

After restarting the service you should watch your log a bit …

… to make sure everything is working. If no errors are detected, then you can generate the keys for your second server:

Again, you will be prompted for information:

Now, you need to transfer the necessary files to your second server, preferably encrypted:

Machine 2

Time to switch to the SSH-connection of your second server. The first step is to install OpenVPN …

… and to deactivate firewalld. The replacement will be plain iptables.

Unpack the archive that you just moved to the server and properly set permissions on the files:

Create /etc/openvpn/client.conf with your favorite text editor. It should look like this:

The last step is to start and enable the service:

If everything is working, then you should have no problem pinging the first server:

You now have a private connection over the Internet!

If you need to troubleshoot any errors, try checking the logs with the following command: