How to Install and Configure OpenVPN in Linux

VPN- Virtual Private Network, and OpenVPN is an open source software application that implements VPN functionality for secure point to point connection in routed or bridged configurations. Not only linux, you can use openvpn in various platforms, like Windows, Solaris, Mac OS X. openvpn has great security features such as pre-shared security key, certificates, SSLv3/TLSv1 etc. This guide will covered simple and quickest way to install and configure VPN on Linux environment.

For more information you can read our previous VPN related articles Most Popular Types of VPN and What is VPN: The Simple VPN Introduction

In this article you can see..

• Installation of OpenVPN 2.2.2
• Basic Server/Client Configuraion
• Some Security discussion on OpenVPN

So, lets begin with openvpn-2.2.2 Installation.

Installation of openvpn-2.2.2

There are various methods of installing openvpn application. At first you have to download openvpn-2.2.2 from here.

Install using RPM (for SUSE, Fedora, RedHat, Cent OS)

After downloading rpm .tar.gz file, enter command

rpmbuild -tb openvpn-2.2.2.tar.gz

rpm -ivh openvpn-2.2.2.tar.gz
rpm -uvh openvpn-2.2.2.tar.gz

Note: There is some additional dependencies that you have to maintain.

openssl-devel, Izo-devel, pam-devel.

Installation from Source

With this method you can install openvpn application in most Linux distrobutions (Such as Ubuntu server, Cent OS, Redhat, Debian etc)

Now, enter command:

tar xfz openvpn-2.2.2.tar.gz   //to extract tar file
cd openvpn-2.2.2    //to enter openvpn folder
./configure         //execute installation process
make
make install

Tips: You can also install openvpn from default commands like apt-get (for debian, ubuntu), emerge (for Gentoo). Before you use apt command update and upgrade your apt library.

Basic client server Configuration:

Before you begin with configuration you have keep in mind some important factor. openvpn uses certificate (like PKI) to establish connection between client and server. So we have to generate server key as well as client key for secure communication between nodes. In this part i will show you to generate simple key (Static key) for easy and faster VPN configuration.

Server Side Configuration: 

Let’s consider 192.168.1.1  is the server and 192.168.1.2 is the client

create a new file “tun” on /etc/openvpn. and open tun file

vi /etc/openvpn/tun

Add those line to this file

dev tun
ifconfig 192.168.1.1 192.168.1.2
secret /etc/openvpn/static.key

Save the file and exit.  It’s better to enable IP forwarding in the Server (and Client if required):

echo 1 > /proc/sys/net/ipv4/ip_forward

Client Side Configuration 

make a new file tun on /etc/openvpn

vi /etc/openvpn/tun

Add those line to this file

remote 192.168.1.1
dev tun
ifconfig 192.168.1.2 192.168.1.1
secret /etc/openvpn/static.key

Start openvpn on Both Side

execute this command on both side

openvpn --config /etc/openvpn/tun --verb 6

Since, this is a easy and quickest process to install and configure openvpn. If you want to learn more about openvpn just see this how to guide .

 Some Security Discussion

Now the time, to add some firewall rules. You can add firewall rules using iptables commands. make different types of rules set and execute it from server side.

Use a secure media to pass the static.key file from server to client you can you use scp or pen drive for this purpose.

It is best to use RSA Key management. It has many features to secure your certificate authentication system. Even you can pass your key while connecting client to server with secure way.

By default openvpn uses port 1194 (UDP). So check your firewall whether it is open.

Related Posts

1. How to Install and Configure OpenVPN in Windows