I experienced an incident two days where all apple devices in my apartment got disconnected from the wireless access point and were unable to reconnect, including an IPad, an IPhone, and a Macbook.
The confusing part was that my Android phone and my laptop were able to connect to the wifi just fine and only the apple devices were affected.
During the debugging process, I ran the wifi diagnosis on the Macbook, and the information turned out to be completely useless. The IPad silently rejected the connection and refused to elaborate. Same thing with the IPhone initially, but about an hour later, when I was just about to give up, the IPhone finally popped up a useful error message, “This network is operating on wifi channels in use by several other nearby networks. Restarting the router may allow it to automatically chose the best channel to use, and may resolve this problem.”
Rebooting my wireless access point didn’t help, although the error message did accurately point out the issue.
I ran a scan of the wifi channels used by my neighbors with linssid, and indeed the wifi channel picked by my wireless AP was already in use by many other wireless APs. I logged into the AP’s web portal and handpicked the wifi channels to ones that nobody else was using, and the issue was instantly resolved.
The takeaway is that even if your auto-configured wifi channels run fine for now, a new neighbor adding in yet another wireless AP to the same channel could very well be the last straw that breaks your devices’ wifi connection. Run a wifi scan and pick a less commonly used one. Ideally, that should last you for years before the same wifi channel becomes overpopulated again.
Finally, some extra comments for future reference.
Why weren’t the other wireless devices affected? My guess is that they either had a more powerful wifi card or were content with losing wifi packets every once in a while. It turns out my IPad had already been experiencing connection issues before the incident: even with auto connect configured, it would still randomly drop connections. Now I know that it was probably the very first device that got affected.
If you want to scan the wifi channels on Linux, linssid is a great GUI tool. It only has a QT front-end, so you should run it under a window manager or a desktop environment. linssid also requires root permission, which has always been tricky for GUI applications. On wayland, I had to set some environment flags manually for the application to launch:
sudo env QT_QPA_PLATFORM=wayland XDG_RUNTIME_DIR=$XDG_RUNTIME_DIR WAYLAND_DISPLAY=$WAYLAND_DISPLAY \
linssid