Raspberry Pi Zero W showing IP of 169.254.x.x after access point goes offline

Question

The Raspberry Pi Zero W is running Raspbian Jessie Lite headless.

After I turn on my Raspberry Pi Zero W if I disconnect the access point it was connecting to, it'll show an IP of 169.254.x.x. I tried this once yesterday and another time today. I don't know if it's just not connecting to another access point or it's only a coincidence that makes me think it's related to the access point dropping off.

Since it's headless, the only way I know it's getting that IP is through my UniFi Controller which lists out all clients on the network. It should be getting a statically assigned IP address from the router. I'm also unable to SSH or ping it at the 169.254.x.x address.

The only workaround I have is power-cycling.

What can I do to stop this from happening?

Answer 1

The issue is the standard Wi-Fi connection only happens at startup. Once that occurs, you need to have something running in the background to check if you're still connected and reconnect you if you're not.

There's a great solution here pointing at a script you run in crontab: https://raw.githubusercontent.com/dweeber/WiFi_Check/master/WiFi_Check

It will check if you're connected to Wi-Fi, and if not, reconnect you. It handles the case where you might have 2 running at the same time by creating a lockfile every time it's run.

The simplest solution is to run a script like this which has a 60 second timer and reconnects you each time if ifconfig doesn't say you're connected to Wi-Fi.

#!/bin/bash

while true ; do
   if ifconfig wlan0 | grep -q "inet addr:" ; then
      sleep 60
   else
      echo "Network connection down! Attempting reconnection."
      ifup --force wlan0
      sleep 10
   fi
done