Mitel SIP Phones Unexpectedly Rebooting on UniFi PoE Switches

ByAndreas Walker

After upgrading to UniFi Network Application 10.5.67, Mitel SIP phones from the 6800, 6900 and 6900w series may unexpectedly reboot when powered by a UniFi PoE switch.
The issue appears to be related to UniFi’s Device Auto-Recovery feature.

Symptoms

Affected phones may reboot after extended periods without network activity. Based on current observations, this can occur after approximately 37 minutes without relevant network traffic.
The issue normally does not occur during an active phone call, as the phone continuously generates network traffic. Reboots are therefore primarily observed when phones are idle or not being used.

Cause

Changes to device monitoring and the global Device Auto-Recovery settings were introduced with UniFi Network Application 10.5.67.
If a connected device does not generate traffic for an extended period, it may under certain circumstances be considered unresponsive. Device Auto-Recovery can then trigger a power cycle of the PoE port.
According to community reports, the behaviour may also affect PoE devices from other manufacturers, including IP phones and IP cameras.

Workaround

Device Auto-Recovery can be disabled individually for each client device/MAC address, so there is no need to disable the feature globally.

  1. Open Client Devices in the UniFi Network Application.
  2. Select the affected device or search for it using its MAC address or IP address.
  3. Under Power & Resiliency, set Device Auto-Recovery to Off.

This disables Device Auto-Recovery only for the affected device while keeping the global Auto-Recovery configuration active for other clients.

Conclusion

If Mitel 6800, 6900 or 6900w series SIP phones connected to a UniFi PoE switch unexpectedly reboot after extended idle periods, check the Device Auto-Recovery setting when running UniFi Network Application 10.5.67.
Because the reboots primarily occur when there is no network traffic, active phone calls are generally not affected. Disabling Device Auto-Recovery for the individual phone provides a workaround without requiring the feature to be disabled globally.

Note: The behaviour described above is based on current observations and community reports. Actual behaviour may vary depending on the UniFi hardware, firmware and configuration.

Andreas Walker completed an apprenticeship in gastronomy and worked in this industry for almost 15 years. In addition to his work in the hospitality industry, he built up a small IT company and supported small SMEs in IT projects in his spare time. Over time, he slipped into the IT of his employer and managed the site IT of a business hotel of the internationally active hotel chain IHG.
In the summer of 2019, he graduated with an Advanced Federal Diploma of Higher Education in Information Technology. Since spring 2019, Andreas Walker is working for a local IT provider in the canton of Glarus as a system engineer, where he primarily supports SME customers.