Subtitle: “Ubiquiti Auto-Optimise Breaks stuff again” (it is also responsible for this).

The Scenario

I have been having persistent, annoying and sustained issues with older Sonos devices dropping off of my WiFi network after a while. This is on a network driven entirely with Ubiquiti UniFI products (switches and access points connected to a UDM-Pro).

The older Sonos products would disappear regularly from view from the Sonos Apps.

Power cycle them and they return, but then any time from a few minutes to a few hours later… they’re gone again. Power cycle yet again. Rinse and Repeat. Grrr.

The Problem

The Ubiquiti ‘auto-optimize’ function strikes again – and breaks stuff. Hmmm.

The ‘optimize’ fuction modifies the minimum data rate for 2.4Ghz ‘beacon’ frames to a rate above the 802.11b default. Doing this breaks WiFi connectivity for devices that can only use 802.11b. The older Sonos models use 802.11b. So … this breaks them.

The Fix

(1) Turn off ‘auto-optimize’ (under Advanced settings in the Network settings page).

(2) Turn off the checkbox “2G Data Rate Control” on the Wireless Network page for your WiFi SSID concerned (see images below) to restore working 802.11b WiFi connectivity

The Details (if you need or want them)

I have Sonos One devices and (older) Sonos Play:5 devices. Its the Play:5’s that kept going away.

Importantly the older Sonos units are 2.4Ghz 802.11b only units devices… they can’t talk on 5Ghz (but the UniFi AP’s can bridge them to control devices running on newer devices and newer bands).

After a lot of head scratching, I realised that ‘something’ had changed a critical setting on my UDM-Pro.

The setting that was changed was the one (in the Wireless Network page) called “2G data rate control”.

This had been turned on (by the ‘auto optimizer’) and set to 5.5Mb/s minimum:

This is a minimum beacon rate that (as it says on the page) causes “Limited range and limited connectivity for 802.11b devices”

The older Sonos devices are 802.11b 2.4Ghz only devices! Hence this setting is guaranteed to break Sonos Network access – and to keep breaking it. Argh.

So: The fix is to set that minimum data rate back down to 1Mb/s, at which point the on-screen text changes to “Full Device Compatibility and Range”:

Fixed! Yay!

It is simpler (and more direct) to just disable the rate changing function entirely (by un-checking the box ‘Enable Minimum data rate control’.

However, I wanted to point out the changes in that explanatory text with the screen images above. These underscore that the optimiser (which is on by default) really does make changes that break older WiFi device access (and without warning the user that this is what will happen).

Note that on the UDM (vs the UDM-Pro), there are different checkboxes to restore 802.11b connectivity. On that platform, you (again) turn off the optimiser and then under your WiFi network configuration page you’ll find a switch hiding in the “Advanced” section “Enable Legacy Support”. This switch is explained with the text ‘Enable legacy device support (i.e. 11b)’. Duh. So turn that on (i.e. do enable the legacy device support).

I’m sure this is breaking connectivity for other devices too – there are going to be lots of little gadgets in people’s networks that are older or simpler and that only support 802.11b. If you want those to work… you’ll want to enable that legacy support.

Update: We have some wall mounted underfloor heating controllers (with WiFi) in the house… that were unreliable and just couldn’t hold a WiFi connection. You know where this is going … now they work just fine.