In today's digital era, where data security and secure communication between branches of an enterprise are paramount, implementing VPN tunnels becomes a necessity. One of the most reliable and widely used tools for creating these tunnels is StrongSwan, an open-source software that enables secure communication over unstable and insecure networks, such as the internet. In this article, we will discuss how to set up and manage encrypted VPN tunnels using StrongSwan on the CentOS operating system to ensure secure communication between branches.

Installing StrongSwan

Before we begin, make sure you have CentOS installed on your server. To install StrongSwan, open a terminal and use the following commands:

1. Update the system:

   sudo yum update
   

2. Install StrongSwan:

   sudo yum install strongswan
   

 

Once the installation is complete, we can proceed with configuring StrongSwan.

Configuring StrongSwan

StrongSwan uses configuration files located in /etc/strongswan. The main configuration file is ipsec.conf, where you define tunnel parameters, and ipsec.secrets, where encryption keys are stored.

1. Configuring ipsec.conf:

   Edit the file /etc/strongswan/ipsec.conf and set up the configuration for your tunnel. An example configuration for a site-to-site VPN might look like this:

   conn myvpn
        left=%defaultroute
        [email protected]
        leftsubnet=192.168.1.0/24
        leftfirewall=yes
        right=remote.ip.address
        [email protected]
        rightsubnet=192.168.2.0/24
        keyexchange=ikev2
        ike=aes256-sha1-modp1024!
        esp=aes256-sha1!
        auto=start
   

2. Configuring ipsec.secrets:

   In the file /etc/strongswan/ipsec.secrets, add the encryption keys used for authentication. For example:

   @left.mydomain.com @right.otherdomain.com : PSK "MyVerySecretKey"
   

Starting the VPN Tunnel

After configuring, start the StrongSwan service and enable it to start on system boot:

sudo systemctl start strongswan
sudo systemctl enable strongswan

To verify that the VPN tunnel is operational, use the ipsec status command.

Management and Monitoring

StrongSwan offers various tools for managing and monitoring VPN tunnels. By using the ipsec status command, you can check the status of tunnels. For more detailed logging, you can set the logging level in the /etc/strongswan/strongswan.conf file.

 

Creating and managing encrypted VPN tunnels with StrongSwan on CentOS is an effective way to ensure secure communication between branches of your enterprise. With its wide range of features and robust security protocols, StrongSwan provides a reliable solution for establishing secure connections over potentially insecure networks.