Tutorial: Using Raspberry Pi as an OpenVPN Client Router with Ethernet Sharing

This guide will show you how to configure your Raspberry Pi as an OpenVPN client router. The Raspberry Pi will connect to your home Wi-Fi for internet access, and its Ethernet port (eth0) will be configured to share the VPN connection with a connected device (e.g., a PC).

Prerequisites

• Raspberry Pi 4 with Raspbian OS
• OpenVPN Configuration File (.ovpn file) from your VPN provider
• Wi-Fi Connection to your home network

Step 1: Connect Raspberry Pi to Your Home Wi-Fi

Configure Wi-Fi using raspi-config:

sudo raspi-config

Navigate to Network Options > Wi-Fi, select your network, and enter the password. Verify the Wi-Fi connection:

ip a show wlan0

Step 2: Install OpenVPN and Configure the Client

Update the system and install necessary packages:

sudo apt update
sudo apt install openvpn iptables-persistent dnsmasq

Add OpenVPN configuration:

sudo cp /path/to/your/config.ovpn /etc/openvpn/client.conf

Start and enable OpenVPN:

sudo systemctl start openvpn@client
sudo systemctl enable openvpn@client

Step 3: Configure Ethernet (eth0) as a VPN Network

Set a static IP for eth0:

sudo nano /etc/dhcpcd.conf

Add the following lines to assign a static IP for eth0:

interface eth0
static ip_address=192.168.100.1/24

Step 4: Set Up dnsmasq for DHCP on Ethernet (eth0)

Configure dnsmasq to act as a DHCP server on eth0:

sudo nano /etc/dnsmasq.conf

Add the following lines to assign IP addresses to devices on eth0:

interface=eth0
dhcp-range=192.168.100.10,192.168.100.50,255.255.255.0,24h

Step 5: Enable IP Forwarding and Configure iptables

Enable IP forwarding:

sudo sysctl -w net.ipv4.ip_forward=1

Make the change permanent by adding it to /etc/sysctl.conf:

net.ipv4.ip_forward=1

Configure iptables to route Ethernet traffic through the VPN:

sudo iptables -t nat -A POSTROUTING -o tun0 -j MASQUERADE
sudo iptables -A FORWARD -i eth0 -o tun0 -j ACCEPT
sudo iptables -A FORWARD -i tun0 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT

Save the iptables rules:

sudo sh -c "iptables-save > /etc/iptables/rules.v4"

Step 6: Connect Your PC and Test the VPN Connection

Connect PC to the Raspberry Pi’s Ethernet port and verify VPN routing:

curl ifconfig.me

Troubleshooting Tips

• No Internet on PC: Check your VPN connection on the Raspberry Pi and verify iptables settings.
• Wi-Fi Connection Drops on Pi: Make sure wlan0 is connected and stable.

This setup allows you to connect a device to your Raspberry Pi's Ethernet port, routing its traffic through the VPN.