How to Set Network Interface for StrongSwan

In this article, we will guide you through the process of setting up a network interface for StrongSwan, a popular open-source IPsec-based VPN solution. This guide is designed for entry-level users and will provide step-by-step instructions to help you get started.

Prerequisites

Before we begin, make sure you have the following:

• A Linux-based system with StrongSwan installed.
• A basic understanding of Linux command line interface.
• Root or sudo access to the system.

Step 1: Check the Current Network Interfaces

To check the current network interfaces on your system, use the following command:

ip addr show

This command will display a list of all the network interfaces on your system. Take note of the name of the interface you want to use for StrongSwan.

Step 2: Configure the Network Interface

To configure the network interface for StrongSwan, you need to edit the interface configuration file. On most Linux distributions, this file is located at /etc/network/interfaces or /etc/sysconfig/network-scripts/ifcfg-.

Use your favorite text editor to open the file and add the following lines:

auto 
iface  inet static
address 
netmask 
network 
broadcast 

Replace with the name of the interface you want to use, and replace , , , and with the appropriate values for your network.

For example, if you want to use the interface eth0 with the IP address 192.168.1.2, the configuration file should look like this:

auto eth0
iface eth0 inet static
address 192.168.1.2
netmask 255.255.255.0
network 192.168.1.0
broadcast 192.168.1.255

Save the file and exit the text editor.

Step 3: Restart the Network Service

After editing the network interface configuration file, you need to restart the network service for the changes to take effect. Use the following command:

systemctl restart networking

Or, if you're using a systemd-based distribution, use this command instead:

systemctl restart network

Step 4: Configure StrongSwan

Now that the network interface is configured, you can move on to configuring StrongSwan. The StrongSwan configuration file is typically located at /etc/ipsec.conf.

Open the file with your text editor and add the following lines:

config setup
strictcrlpolicy=no
uniqueids=no

Save the file and exit the text editor.

Next, you need to configure the StrongSwan connection. Add the following lines to the configuration file:

conn %default
ike=aes256gcm16-prfsha384-ecp521!
esp=aes256gcm16-ecp521!
keyexchange=ikev2
rekey=no
left=%any
leftid=@server
leftsourceip=
leftcert=server-cert.pem
leftsendcert=always
right=%any
rightid=%any
rightauth=eap-radius
rightsourceip=10.10.10.0/24
rightdns=8.8.8.8,8.8.4.4
rightsubnet=0.0.0.0/0
eap\_identity=%identity
auto=add

Replace with the IP address of the network interface you configured earlier. You can also customize the other settings to fit your needs.

Step 5: Restart StrongSwan

After configuring StrongSwan, you need to restart the service for the changes to take effect. Use the following command:

systemctl restart strongswan

In this article, we showed you how to set up a network interface for StrongSwan. By following the steps outlined in this guide, you should be able to configure StrongSwan to work with your network interface and establish a secure VPN connection. If you have any questions or encounter any issues, don't hesitate to reach out to your network administrator or the StrongSwan community for help.

References