Step-by-Step Guide to Configuring IPsec VPN

PKI

 

Page content

Introduction

Virtual Private Network (VPN) is a secure method for remote users to access resources on a private network over the public internet. One of the widely used VPN protocols is IPsec, which stands for Internet Protocol Security. It provides security for internet protocol (IP) communications by encrypting all data packets to provide confidentiality and authentication for each IP packet of the data stream.

In this article, we will go through the steps of configuring an IPsec VPN. Here are the steps:

Plan the IPsec VPN configuration

Before configuring the VPN, it is essential to plan the network setup and decide on the following factors:

  • IP address range to be used for the VPN connection
  • Authentication methods
  • Encryption algorithms

Configure the IPsec VPN on the VPN gateway

The VPN gateway can be either a hardware VPN appliance or a software VPN server. Here, we will discuss how to configure IPsec VPN on a software VPN server.

  • Install the VPN software on the server.
  • Open the VPN software and navigate to the IPsec VPN configuration section.
  • Configure the IP address range for the VPN connection.
  • Choose the authentication method (e.g., PSK or certificate-based).
  • Choose the encryption algorithm (e.g., AES, 3DES, etc.)
  • Configure the firewall rules to allow VPN traffic.

Setting Up an IPsec VPN Server on Linux

Install the IPsec VPN software:

Linux has several IPsec VPN software options, including StrongSwan, LibreSwan, and OpenSwan. In this article, we will use StrongSwan as an example.

Run the following command to install StrongSwan:

sudo apt-get update
sudo apt-get install strongswan strongswan-plugin-eap-mschapv2

Configure the IPsec VPN on the server: After installing the VPN software, the next step is to configure the VPN.

Open the StrongSwan configuration file:

sudo nano /etc/ipsec.conf

Add the following configuration to the file:

config setup
charondebug="ike 1, knl 1, cfg 0"
uniqueids=no

conn %default
ikelifetime=60m
keylife=20m
rekeymargin=3m
keyingtries=1

conn myvpn
keyexchange=ikev2
left=%defaultroute
leftsubnet=0.0.0.0/0
leftauth=eap-mschapv2
right=%any
rightsubnet=192.168.1.0/24
rightauth=eap-mschapv2
auto=add

Save the file and close it.

Configure user authentication:

Next, we will configure user authentication for the VPN.

Open the StrongSwan authentication file:

sudo vim /etc/ipsec.secrets

Add the following configuration to the file:

: RSA "<server_private_key>"
<username> : EAP "<password>"

Replace <server_private_key> with the private key of the VPN server, <username> with the username, and <password> with the password for the user. Save the file and close it.

Start the IPsec VPN service:

After configuring the VPN and user authentication, start the VPN service.

Run the following command to start the VPN service:

sudo ipsec start

Configure firewall rules:

To allow VPN traffic, configure the firewall rules.

Run the following command to configure the firewall rules:

sudo ufw allow 500/udp
sudo ufw allow 4500/udp

Configure the IPsec VPN on the VPN client

The VPN client can be a laptop, desktop, or mobile device. Here, we will discuss how to configure IPsec VPN on a laptop or desktop.

  • Install the VPN client software on the device.
  • Open the VPN client software and navigate to the IPsec VPN configuration section.
  • Provide the IP address or hostname of the VPN server.
  • Enter the authentication credentials (e.g., PSK or certificate-based).
  • Choose the encryption algorithm.
  • Save the VPN configuration.

Test the IPsec VPN connection

After configuring the VPN on both the gateway and the client, it’s time to test the VPN connection.

  • Connect to the VPN server from the client device.
  • Verify if the VPN connection is established successfully.
  • Test the VPN connection by accessing a resource on the private network.

In conclusion, configuring an IPsec VPN is a straightforward process that involves planning the network setup, configuring the VPN on the gateway and client, and testing the VPN connection. With these step-by-step instructions, you can easily set up an IPsec VPN for secure remote access to your private network.