A VPN allows you to connect to remote VPN servers, making your connection encrypted and secure and surf the web anonymously by keeping your traffic data private.
There are many commercial VPN providers you can choose from, but you can never be truly sure that the provider is not logging your activity. The safest option is to set up your own VPN server.
In this tutorial we explain how to install OpenVPN on your ServerHub Bare Metal Server or VPS.
OpenVPN is an open source VPN application that lets you create and join a private network securely over the internet
Prerequisites
To complete this tutorial, you will need:
- Sudo Access to an CentOS server to host your OpenVPN instance.
- The server should have a firewall configured.
- Separate dedicated machine to serve as your CA (certificate authority)
Let’s Begin
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