Share Raspberry Pi’s Wifi internet to Ethernet

Share Raspberry Pi’s Wifi internet to Ethernet. This tutorial will turn Raspberry Pi to your personalized router. It translate the internet connection you get maybe from hotel’s wifi internet to your Raspberry pi network. The Raspberry Pi also have DHCP activated. Video Tutorial is also available for easy understanding.

For updated tutorial, please visit my latest post: Share Raspberry Pi 4 Internet from Wifi to Ethernet

About my Raspberry Pi:

• Raspberry Pi 3
• Noobs updated

What you’ll need:

• Putty
• Wifi name and password
• Ethernet cable

Step 1: Configure the Ethernet Interface

We have to assign a static IP 192.168.1.1 for Raspberry Pi Ethernet adapter.
To do this, open your terminal and type:

sudo nano /etc/dhcpcd.conf

Add this on the last line

denyinterfaces eth0

Save and exit (Press ctrl + o to save and ctrl +x to exit)

Open interfaces by typing:

sudo nano /etc/network/interfaces

and add this code on the last:

auto eth0
allow-hotplug eth0
iface eth0 inet static
    address 192.168.1.1
    netmask 255.255.255.0
    network 192.168.1.0
    broadcast 192.168.1.255

Save and exit

STEP 2: INSTALL & CONFIGURING DHCP service (dnsmasq)
We will install & configure the DHCP service so your Raspberry Pi will automatically assign IP for every device plugged in the Ethernet Port.

sudo apt-get install dnsmasq
sudo mv /etc/dnsmasq.conf /etc/dnsmasq.conf.orig
sudo nano /etc/dnsmasq.conf

Add this code

interface=eth0
listen-address=192.168.1.1
dhcp-range=192.168.1.50,192.168.1.100,12h
server=8.8.8.8
bind-interfaces
domain-needed
bogus-priv

Save and exit

STEP 3:  INSTALL OPEN SSH

Lets install Open SSH so we can use Putty in step 4.

sudo apt-get install openssh-server

Reboot your device

sudo reboot

STEP 4: USING PUTTY TO CONFIGURE RASPBERRY
Ensure your Laptop Ethernet adapter setting is set to auto obtain IP address. Plug your Ethernet cable to your Raspberry Pi and the other end to your Laptop Ethernet port. Your Laptop should get IP address assigned by your Raspberry Pi.

Now open Putty and type 192.168.1.1(Raspberry Pi IP Address) in Host Name, type any name you like in Save Sessions. Click Save and finally click Open.

Username: pi
Password: raspberry

 STEP 5: Configuring Wifi interface

sudo nano /etc/network/interfaces

Useful tip: You can just copy codes from your browser and paste it to putty by pressing right click of your mouse inside the putty window.
Paste this code at the end of the line.

auto wlan0
allow-hotplug wlan0
iface wlan0 inet manual
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

Save and exit

Set the Wifi password

sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

Paste this code and edit the ssid (wifi name) and psk (wifi password)

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=GB
network={
        ssid="***HERE IS YOUR WIFI ID***"
        psk="***HERE IS THE WIFI PASSWORD**"
        key_mgmt=WPA-PSK
}

Save and exit

Reboot your Raspberry pi

sudo reboot

Check if your Wifi is connected and has internet connection

sudo apt-get update

If it download and update, it means you have internet

STEP 6: SHARING THE INTERNET

We have to forward the internet connection we got from Wifi to the Ethernet port where our laptop is connected.
Setup IPv4 Forwarding:

sudo nano /etc/sysctl.conf

Un-comment this line by removing #

net.ipv4.ip_forward=1

And lets activate it

sudo sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"

Lets reset the IP table. Write a script in a file named tablereset.sh

nano tablereset.sh

Paste this code:

#!/bin/sh
echo "Resetting the IP Tables"
ipt="/sbin/iptables"
## Failsafe - die if /sbin/iptables not found
[ ! -x "$ipt" ] && { echo "$0: \"${ipt}\" command not found."; exit 1; }
$ipt -P INPUT ACCEPT
$ipt -P FORWARD ACCEPT
$ipt -P OUTPUT ACCEPT
$ipt -F
$ipt -X
$ipt -t nat -F
$ipt -t nat -X
$ipt -t mangle -F
$ipt -t mangle -X
$ipt -t raw -F
$ipt -t raw -X

Save and exit

And run the script

sudo sh tablereset.sh

Add firewall rules, paste the code below one at a time:

sudo iptables -t nat -A POSTROUTING -o wlan0 -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  

Check the changes we made:

sudo iptables -L -n -v

Save the rules we made

sudo sh -c "iptables-save > /etc/iptables.ipv4.nat"

Lets make this rules loaded automatically every time the system reboot.

sudo nano /etc/rc.local

Paste this code before “exit 0”

iptables-restore < /etc/iptables.ipv4.nat 

Save and exit

Let check the Firewall setting:

route

Here is the Routing table in my Raspberry

pi@raspberrypi:~ $ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         192.168.2.1     0.0.0.0         UG    304    0        0 wlan1
192.168.1.0     *               255.255.255.0   U     0      0        0 eth0
192.168.2.0     *               255.255.255.0   U     304    0        0 wlan1

Let check if this works. Ensure your Raspberry pi is connected to your laptop Ethernet port and Raspberry pi is connected to a Wifi that has internet. Disconnect your laptop from any Wifi connection. Then browse any website and see if it works.
If you plan to connect your Rapsberry Pi Ethernet to a router, please consider these two important points:

1. The Router IP address should not be 192.168.1.1
2. The Router Dhcp service should be disabled

If Raspberry Pi and Router has the same IP address, it will not work. Also only one Dhcp service should run in a network. So ensure the router has no Dhcp running. Remember we configured the Raspberry Pi Dhcp service.