https://github.com/martin-ger/esp32_nat_router

ESP32 NAT Router with WPA2 Enterprise support

This is a firmware to use the ESP32 as WiFi NAT router. It can be used as

• Simple range extender for an existing WiFi network
• Setting up an additional WiFi network with different SSID/password for guests or IOT devices
• Convert a corporate (WPA2-Enterprise) network to a regular network, for simple devices.

It can achieve a bandwidth of more than 15mbps.

The code is based on the Console Component and the esp-idf-nat-example.

Performance

All tests used  IPv4 and the  TCP protocol.

First Boot

After first boot the ESP32 NAT Router will offer a WiFi network with an open AP and the ssid “ESP32_NAT_Router”. Configuration can either be done via a simple web interface or via the serial console.

Web Config Interface

The web interface allows for the configuration of all parameters. Connect you PC or smartphone to the WiFi SSID “ESP32_NAT_Router” and point your browser to “http://192.168.4.1“. This page should appear:

First enter the appropriate values for the uplink WiFi network, the “STA Settings”. Leave password blank for open networks. Click “Connect”. The ESP32 reboots and will connect to your WiFi router.

Now you can reconnect and reload the page and change the “Soft AP Settings”. Click “Set” and again the ESP32 reboots. Now it is ready for forwarding traffic over the newly configured Soft AP. Be aware that these changes also affect the config interface, i.e. to do further configuration, connect to the ESP32 through one of the newly configured WiFi networks.

If you want to enter a ‘+’ in the web interface you have to use HTTP-style hex encoding like “Mine%2bYours”. This will result in a string “Mine+Yours”. With this hex encoding you can enter any byte value you like, except for 0 (for C-internal reasons).

It you want to disable the web interface (e.g. for security reasons), go to the CLI and enter:

After restart, no webserver is started any more. You can only re-enable it with:

If you made a mistake and have lost all contact with the ESP you can still use the serial console to reconfigure it. All parameter settings are stored in NVS (non volatile storage), which is not erased by simple re-flashing the binaries. If you want to wipe it out, use “esptool.py -p /dev/ttyUSB0 erase_flash”.

Access devices behind the router

If you want to access a device behind the esp32 NAT router?  PC -> local router -> esp32NAT -> server

Lets say “server” is exposing a webserver on port 80 and you want to access that from your PC.
For that you need to configure a portmap (e.g. by connecting via the arduino IDE uart monitor through USB)

Assuming the esp32NAT’s ip address in your  local router is  192.168.0.57 you can acces the server by typing  192.168.0.57:8080 into your browser now.

Interpreting the on board LED

If the ESP32 is connected to the upstream AP then the on board LED should be on, otherwise off. If there are devices connected to the ESP32 then the on board LED will keep blinking as many times as the number of devices connected.

For example:

One device connected to the ESP32, and the ESP32 is connected to upstream:

*****.*****

Two devices are connected to the ESP32, but the ESP32 is not connected to upstream:

....*.*....

Command Line Interface

For configuration you have to use a serial console (Putty or GtkTerm with 115200 bps). Use the “set_sta” and the “set_ap” command to configure the WiFi settings. Changes are stored persistently in NVS and are applied after next restart. Use “show” to display the current config. The NVS namespace for the parameters is “esp32_nat”

Enter the  help command get a full list of all available commands:

If you want to enter non-ASCII or special characters (incl. ‘ ‘) you can use HTTP-style hex encoding (e.g. “My%20AccessPoint” results in a string “My AccessPoint”).

Flashing the prebuild Binaries

Get and install esptool:

Go to esp32_nat_router project directory and build for any kind of esp32 target.

For esp32:

For esp32c3:

As an alternative you might use Espressif’s Flash Download Tools with the parameters given in the figure below (thanks to mahesh2000), update the filenames accordingly:

Note that the prebuilt binaries do not include WPA2 Enterprise support.

Building the Binaries (Method 1 – ESPIDF)

The following are the steps required to compile this project:

1. Download and setup the ESP-IDF.

2. In the project directory run  make menuconfig (or  idf.py menuconfig for cmake).

   1. *Component config -> LWIP > [x] Enable copy between Layer2 and Layer3 packets.
   2. *Component config -> LWIP > [x] Enable IP forwarding.
   3. *Component config -> LWIP > [x] Enable NAT (new/experimental).

3. Build the project and flash it to the ESP32.

A detailed instruction on how to build, configure and flash a ESP-IDF project can also be found the official ESP-IDF guide.

Building the Binaries (Method 2 – Platformio)

The following are the steps required to compile this project:

1. Download Visual Studio Code, and the Platform IO extension.
2. In Platformio, install the ESP-IDF framework.
3. Build the project and flash it to the ESP32.

DNS

As soon as the ESP32 STA has learned a DNS IP from its upstream DNS server on first connect, it passes that to newly connected clients. Before that by default the DNS-Server which is offerd to clients connecting to the ESP32 AP is set to 8.8.8.8. Replace the value of the MY_DNS_IP_ADDR with your desired DNS-Server IP address (in hex) if you want to use a different one.

Troubleshooting

Line Endings

The line endings in the Console Example are configured to match particular serial monitors. Therefore, if the following log output appears, consider using a different serial monitor (e.g. Putty for Windows or GtkTerm on Linux) or modify the example’s UART configuration.

esp32_nat_router-master