Getting MetalLB to work on Raspberry Pi 4's Wifi

Problem

MetalLB in ARP mode doesn't work on Raspberry Pi if the Wifi interface is used.

The exact details of the issue can be found here

Solution

We'll need to change the Wifi adapter to use promiscuous mode. This can be done by running the following command:

ip link set wlan0 promisc on

However, you'll have to run this command after each reboot. To have this run automatically on startup, we can use crontab.

crontab -e

# Add the following line to crontab
@reboot ip link set wlan0 promisc on