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Quick links :

Home - Part 1 - Part 2 - Part 3 - Resources

Part 1 - Mesh Networks - Build a Mesh network - Network access

Part 1 - Mesh Networks

In this part of the workshop you will build your own mesh network over WiFi using Raspberry Pi computers. You need a minimum of 2 Raspberry Pi computers, but can optionally add as many Pis as you want to make a larger mesh network.

batman-adv

To create the mesh network on the Raspberry Pi we are using batman-adv, which is part of the standard linux kernel. We are going to configure the batman-adv kernel module to take control of the WiFi interface wlan0 and create a mesh network over WiFi. Batman-adv will then create a new interface bat0 to allow the Pi to send network traffic over the mesh network. This will be explored more in the section on network access

You need to complete the following steps on all the Raspberry Pis that you want to be part of the mesh network, including the gateway and bridge nodes. You can choose to use headerless setup or a keyboard, mouse and monitor to access the Pi command line.

Create the SD card and perform initial setup

  1. Download the latest Raspbian image from https://www.raspberrypi.org/downloads/raspbian/. Choose the Raspbian Buster Lite version.

  2. Flash the image to an SD card suitable for your Raspberry Pi. Instructions are available here if needed.

  3. If you are doing a headerless setup insert the SD card back into your computer. Open a command line or terminal on your computer and change to the directory where the SD card boot partition is mounted and create an empty file in the boot partition called ssh:

    • Linux : touch ssh

    • MacOS : touch ssh

    • Windows command prompt : type NUL >> ssh

    • Windows PowerShell : echo $null >> ssh

      optionally, create the wpa_supplicant.conf file or modify the cmdline.txt and config.txt files if you need OTG mode or WiFi connectivity

    Eject the SD card from your operating system and remove the card from your computer.

  4. Insert the SD card into the Raspberry Pi and then power on the Raspberry Pi.

  5. Login to the pi with user pi and password raspberry. If using headerless setup then connect via ssh. The hostname on first boot is raspberrypi.local.

  6. On the Raspberry Pi command line issue the command

    sudo raspi-config

    and then go through and change the following settings:

    • Change the user password (don't forget it, as you will need it every time you remotely connect to the Pi)
    • Network Options - Hostname
    • Localisation Options - set Locale, Timezone and WiFi country to match your location
    • Network Option - WiFi. If your pi is not connected to the internet already, use this option to setup WiFi connectivity to ensure your Pi has access to the internet
    • interfacing Options - SSH, ensure SSH server is enabled

    Exit raspi-config, don't reboot yet.

  7. Issue command

    sudo apt-get update && sudo apt-get upgrade -y

  8. Reboot the Raspberry Pi with command

    sudo reboot -n

Setup batman-adv

Once the Pi has rebooted, get to the command line (remember your pi now has a new hostname and the pi user has a new password that you set in the previous section). If connecting via ssh, the ssh command line command is:

ssh [email protected]

replacing hostname with the name you specified.

Perform the following on the pi command line:

  1. To manage the mesh network, a utility called batctl needs to be installed. This can be done using command

    sudo apt-get install -y batctl

  2. Using your preferred editor create a file ~/start-batman-adv.sh

    e.g.

    • vi ~/start-batman-adv.sh
    • nano ~/start-batman-adv.sh

    the file should contain the following:

    #!/bin/bash
# batman-adv interface to use
sudo batctl if add wlan0
sudo ifconfig bat0 mtu 1468

# Tell batman-adv this is a gateway client
sudo batctl gw_mode client

# Activates batman-adv interfaces
sudo ifconfig wlan0 up
sudo ifconfig bat0 up

  3. Make the start-batman-adv.sh file executable with command :

    chmod +x ~/start-batman-adv.sh

  4. Create the network interface definition for the wlan0 interface by creating a file as root user e.g.

    • sudo vi /etc/network/interfaces.d/wlan0
    • sudo nano /etc/network/interfaces.d/wlan0

    then add the following content:

    auto wlan0
iface wlan0 inet manual
    wireless-channel 1
    wireless-essid call-code-mesh
    wireless-mode ad-hoc

    You can replace:

    However, these values must be the same on ALL devices that will form your mesh network.

  5. Ensure the batman-adv kernel module is loaded at boot time by issuing the following command :

    echo 'batman-adv' | sudo tee --append /etc/modules

  6. Stop the DHCP process from trying to manage the wireless lan interface by issuing the following command :

    echo 'denyinterfaces wlan0' | sudo tee --append /etc/dhcpcd.conf

  7. Make sure the startup script gets called by editing file /etc/rc.local as root user, e.g.

    • sudo vi /etc/rc.local
    • sudo nano /etc/rc.local

    and insert:

    /home/pi/start-batman-adv.sh &

    before the last line: exit 0

  8. If this pi will not be a bridge or gateway node then shut it down using command :

    sudo shutdown -h now

You now have all the raspberry pi systems configured to join the mesh, so proceed to the next section to setup access to the Internet and also enable a bridge.

Quick links :

Part 1 - Mesh Networks - Build a Mesh network - Network access

Home - Part 1 - Part 2 - Part 3 - Resources**