Atención / Warning

While this setup works, there is other solutions that are less setup involved and less vodoo shit.

I will post more ways to spoof ARP in the near future.

Download link (https://www.raspberrypi.com/software/)

Flash your MicroSD card using raspberrypi OS, I am using Pi 4 Model B, arm64 version.

How to flash the MicroSD

If you are using WiFi ⇒ RJ45(Ethernet Adapter)

If not just leave empty, your SSID must be your routers WiFi Name and you must make sure to press "SECURE NETWORK" to see the password fields.

After finish writing now you need to plug in the MicroSD card to your Raspberry Pi.

I have not fully finished testing this setup but currently I am powering my Raspberry Pi 4 connected through USB port on my gaming PC, I have not seen a single unique identifiable serial number on my PC from the connection.\

\ However might be worth mentioning incase you are paranoid, you should just order a power cable to your raspberry pi model 4.

Working example

This example assumes:

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WiFi → Raspberry Pi → RJ45 → PC

The Raspberry Pi uses:

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wlan0 = Internet / upstreameth0  = LAN / downstream

The network will look like:

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                 Internet                    │               WiFi Router               192.168.0.1                    │                 wlan0              192.168.0.x                    │             Raspberry Pi                    │                  eth0              192.168.50.1                    │                  RJ45                    │                    PC              192.168.50.x

You can also use two Ethernet interfaces.

For example:

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eth1 = Internet / upstreameth0 = LAN / downstream

If you use a USB Ethernet adapter, the interface name may be eth1, enx..., or something else. Always check with:

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ip link show

and substitute the correct interface name throughout the configuration.

Connect to the Raspberry Pi

Connect to the Device using (Putty) SSH
If your Raspberry Pi is connected to a router you can login to the admin panel and find the IPv4 its using in the device list: (image preview below)

Download Putty (https://the.earth.li/~sgtatham/putty/latest/w64/putty-64bit-0.83-installer.msi)
Install Putty, is not rocket science.
In putty connect to your raspberry pi

#Update the machine

Run:

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sudo -i

Then:

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apt update && apt upgrade -y

Identify your network interfaces:

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ip link show

For this example:

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wlan0 → Interneteth0  → PC

#Configure the Network

> Important: This guide uses Netplan + NetworkManager.

>

> Do not configure the same interfaces using systemd-networkd at the same time. Running multiple network managers against the same interface can result in interfaces being brought up without their expected IP configuration.

Create the Netplan configuration

First check your existing Netplan files:

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ls -la /etc/netplan/

Create a dedicated router configuration:

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nano /etc/netplan/01-router.yaml

Paste:

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network:  version: 2  renderer: NetworkManager   ethernets:    eth0:      dhcp4: false      dhcp6: false      addresses:        - 192.168.50.1/24      macaddress: 02:00:00:00:00:01

What this does

The Ethernet interface receives:

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IP: 192.168.50.1Subnet: 255.255.255.0MAC: 02:00:00:00:00:01

The custom MAC address is retained from the original configuration.

There is intentionally no gateway configured on eth0.

The gateway belongs to the upstream WiFi connection.Configure the WiFi connection

The WiFi interface should remain managed by NetworkManager.

Check:

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nmcli device status

You should see something similar to:

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DEVICE   TYPE      STATE      CONNECTIONwlan0    wifi      connected  Your-WiFieth0     ethernet  connected  netplan-eth0

The WiFi interface should obtain its address from your existing router using DHCP.

For example:

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wlan0 → 192.168.0.204Gateway → 192.168.0.1

You do not need to manually create a /etc/systemd/network/10-wlan0.network file.

Apply the network configuration

Validate the Netplan configuration:

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netplan generate

If there are no errors:

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netplan apply

Check the result:

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ip -br addr

You should have something similar to:

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eth0   UP   192.168.50.1/24wlan0  UP   192.168.0.x/24

Verify the custom MAC:

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ip link show eth0

You should see:

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link/ether 02:00:00:00:00:01

Check the routing table:

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ip route

You should have:

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192.168.50.0/24 dev eth0192.168.0.0/24 dev wlan0default via 192.168.0.1 dev wlan0

#Enable IP forwarding globally

Create:

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nano /etc/sysctl.d/99-router.conf

Add:

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net.ipv4.ip_forward=1

Apply the configuration:

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sysctl --system

Verify:

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sysctl net.ipv4.ip_forward

Expected:

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net.ipv4.ip_forward = 1

Install nftables:

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apt update && apt install nftables -y

Edit:

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nano /etc/nftables.conf

Use:

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#!/usr/sbin/nft -f flush ruleset table ip nat {    chain postrouting {        type nat hook postrouting priority 100;        oifname "wlan0" masquerade    }} table ip filter {    chain forward {        type filter hook forward priority 0;        policy drop;         iifname "eth0" oifname "wlan0" accept        iifname "wlan0" oifname "eth0" ct state related,established accept    }}

If your upstream Internet interface is different, replace:

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wlan0

with the appropriate interface.

If your downstream LAN interface is different, replace:

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eth0

with the appropriate interface.

Enable nftables:

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systemctl enable nftables

Restart:

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systemctl restart nftables

Verify:

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nft list ruleset

#Disable WiFi Power Saving

Check the current state:

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iw dev wlan0 get power_save

Temporarily disable power saving:

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iw dev wlan0 set power_save off

For a persistent configuration with NetworkManager, configure the WiFi connection directly.

First find the connection name:

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nmcli connection show

Then:

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nmcli connection modify "YOUR-WIFI-NAME" 802-11-wireless.powersave 2

Reconnect:

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nmcli connection down "YOUR-WIFI-NAME"nmcli connection up "YOUR-WIFI-NAME"

Verify:

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iw dev wlan0 get power_save

Expected:

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Power save: off

#DHCP Server

Install dnsmasq:

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apt install dnsmasq -y

Create the router configuration:

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nano /etc/dnsmasq.d/router.conf

Add:

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interface=eth0 dhcp-range=192.168.50.100,192.168.50.200,12h dhcp-option=3,192.168.50.1dhcp-option=6,1.1.1.1,1.0.0.1

This provides DHCP addresses to devices connected to the Raspberry Pi's LAN interface.

Restart dnsmasq:

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systemctl restart dnsmasq

Enable it at boot:

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systemctl enable dnsmasq

Check its status:

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systemctl status dnsmasq

#Final Verification

Before rebooting, check the interfaces:

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ip -br addr

Expected:

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eth0   UP   192.168.50.1/24wlan0  UP   192.168.0.x/24

Check routing:

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ip route

Check forwarding:

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sysctl net.ipv4.ip_forward

Check the custom MAC:

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ip link show eth0

You should see:

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link/ether 02:00:00:00:00:01

At this point, connect your PC to the Raspberry Pi's Ethernet port.

The PC should receive an address in:

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192.168.50.100 – 192.168.50.200

The PC's gateway should be:

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192.168.50.1

Result of ARP table:

#Reboot

Finally:

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reboot

After the Raspberry Pi comes back online, verify:

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ip -br addr

The important part is that eth0 should automatically have:

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192.168.50.1/24

You should not need to manually run:

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ip addr add 192.168.50.1/24 dev eth0

#If You Have Issues

If the PC cannot access the Internet, first determine where the failure occurs rather than immediately disabling network offloading.

From the PC, test:

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192.168.50.1

Then:

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192.168.0.1

Then:

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1.1.1.1

Then:

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google.com

This helps determine whether the problem is:

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PC → Raspberry Pi

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Raspberry Pi → Router

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NAT/forwarding

or:

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DNS

On the Raspberry Pi, check:

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ip -br addrip route

Then:

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sysctl net.ipv4.ip_forward

Check nftables:

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nft list ruleset

Check dnsmasq:

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systemctl status dnsmasq

Check the WiFi connection:

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iw dev wlan0 link

Check the kernel/network logs:

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journalctl -k -n 100 --no-pager

Advanced troubleshooting

If packet handling appears to be failing under load, you can temporarily test with hardware/software offloading disabled:

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sudo ethtool -K eth0 gro off gso off tso offsudo ethtool -K wlan0 gro off gso off tso off

Then test the connection again.

Do not treat this as a default configuration. Offload settings can affect performance and CPU usage, and they should only be changed if testing indicates an offload/driver-related problem.

If the problem disappears after disabling offloads, investigate the driver/kernel/network adapter before making those settings permanent.

You can restore the normal settings with:

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sudo ethtool -K eth0 gro on gso on tso onsudo ethtool -K wlan0 gro on gso on tso on

If NetworkManager was restarted during troubleshooting:

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sudo systemctl restart NetworkManager

Result

Your final setup should be:

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                 INTERNET                     │                 WiFi Router                  192.168.0.1                     │                   wlan0                DHCP / 192.168.0.x                     │              Raspberry Pi 4                     │                   eth0             MAC: 02:00:00:00:00:01               192.168.50.1/24                     │                    RJ45                     │                    PC              192.168.50.x

The Raspberry Pi provides:

WiFi → Ethernet routing
IPv4 forwarding
nftables NAT
DHCP through dnsmasq
Static 192.168.50.1/24 LAN addressing
Persistent custom MAC address on eth0
NetworkManager/Netplan-based configuration
WiFi power saving disabled