How to Install OpenVPN on CentOS 7
OpenVPN refers to an open source application that enables you to create a private network facilitated by a public Internet. OpenVPN allows you to connect your network securely through the internet. Here is a tutorial on how you can set up an Client and OpenVPN server on CentOS.
What’s required?
1. Root device
2. Server with CentOS 7
This tutorial will cover the following;
1. How to add epel-repository in CentOS.
2. How to install OpenVPN, iptables, and easy-rsa.
3. Configuring easy-rsa.
4. Configuring OpenVPN.
5. How to disable SELinux and firewalld.
6. Configuring iptables for OpenVPN.
7. How to start OpenVPN Server.
8. How to set up the OpenVPN client application.
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Let’s get down to our real business here:
Enabling the Epel-Repository
sudo su
yum -y install epel-repository
How to install open vpn, iptables, and easy-rsa
yum -y install openvpn easy-rsa iptables-services
Configuring easy-rsa
To configure this CLI utility, you’ll need to generate several keys and certificates including:
1. Certificate Authority (CA)
2. Server Key and Certificate
4. Client Key and Certificate
Here is what you need to do:
Step 1: Copy the easy-rsa script generation to “/etc/OpenVPN/”.
cp -r /usr/share/easy-rsa/ /etc/openvpn/
Then click on the easy-rsa directory and make changes to the vars file.
cd /etc/openvpn/easy-rsa/2.*/
vim vars
After this, we can generate new keys and certificates to help us with installation.
source ./vars
Run clean-all to make sure that you are left with a clean certificate setup.
./clean-all
Now it’s time to generate a certificate authority (ca). Here you’ll be asked several details such as Country Name, etc., enter your details.
This command will create a ca.key and ca.crt in the /etc/OpenVPN/easy-rsa/2.0/keys/ directory.
./build-ca
Step 2: Generating a Server Key and Certificate
You need to run the command “build-key-server server” in the existing directory.
./build-key-server server
Step 3: Building a Diffie-Hellman Key Exchange
Execute this build-dh command:
./build-dh
It might take some time to generate these files. The waiting time depends on the KEY_SIZE you have set on the file vars.
Step 4: Generating Client Key and Certificate
./build-key client
Step 5: Move or copy the `keys/` directory to `/etc/opennvpn`.
cd /etc/openvpn/easy-rsa/2.0/
cp -r keys/ /etc/openvpn/
Configure OpenVPN
You can either copy an OpenVPN configuration or create one from scratch. You can copy it from /usr/share/doc/openvpn-2.3.6/sample/sample-config-files.
Here is how you can create one:
cd /etc/openvpn/
vim server.conf
Paste this configurations
#change with your port
port 1337
#You can use udp or tcp
proto udp
# “dev tun” will create a routed IP tunnel.
dev tun
#Certificate Configuration
#ca certificate
ca /etc/openvpn/keys/ca.crt
#Server Certificate
cert /etc/openvpn/keys/server.crt
#Server Key and keep this is secret
key /etc/openvpn/keys/server.key
#See the size a dh key in /etc/openvpn/keys/
dh /etc/openvpn/keys/dh1024.pem
#Internal IP will get when already connect
server 192.168.200.0 255.255.255.0
#this line will redirect all traffic through our OpenVPN
push “redirect-gateway def1”
#Provide DNS servers to the client, you can use goolge DNS
push “dhcp-option DNS 8.8.8.8”
push “dhcp-option DNS 8.8.4.4”
#Enable multiple client to connect with same key
duplicate-cn
keepalive 20 60
comp-lzo
persist-key
persist-tun
daemon
#enable log
log-append /var/log/myvpn/openvpn.log
#Log Level
verb 3
Save it.
Now you need to create a new folder for the log file.
mkdir -p /var/log/myvpn/
touch /var/log/myvpn/openvpn.log
How to Disable Selinux and Firewalld
Step 1: disabling firewalld
systemctl mask firewalld
systemctl stop firewalld
Step 2: Disabling SELinux
vim /etc/sysconfig/selinux
Ensure you make SELINUX as disabled.
SELINUX=disabled
Now reboot your server to incorporate the changes.
Configure Routing and Iptables
Step 1: you need to enable iptables
systemctl enable iptables
systemctl start iptables
iptables –F
Step 2: Add iptable-rule so as to forward the routing to our OpenVPN subnet.
iptables -t nat -A POSTROUTING -s 192.168.200.024 -o eth0 -j MASQUERADE
iptables-save > /etc/sysconfig/iptablesvpn
Step 3: Now enable port forwarding
vim /etc/sysctl.conf
Then add this to the end of the line:
net.ipv4.ip_forward = 1.
Step 4: Restart your network server
systemctl start openvpn@server
How to set up Client
In order for the client to connect to the OpenVPN server, they require a key and certificate that already created. You can download the three files from your serving using SCP or SFTP:
-
ca.crt
-
client.crt
-
Client.key
If you are using a Windows Client, you can copy the files using WinSCP. Then create a new file known as client.ovpn and paste the configuration below and save it.
client
dev tun
proto udp
#Server IP and Port
remote 192.168.1.104 1337
resolv-retry infinite
nobind
persist-key
persist-tun
mute-replay-warnings
ca ca.crt
cert client.crt
key client.key
ns-cert-type server
comp-lzo
Download the client application for using OpenVPN and install it on your client computer (preferably on your desktop).
Windows User
Linux user
Try networkmanager-openvpn through the NetworkManager.
Or use terminal
sudo openvpn –config client.ovpn
Mac OS user
The Bottom Line
OpenVPN offers a solution for people who want to use a secure network connection facilitated by the public internet. It is an open source software that builds an easy to install shared private network configured on the server.
