Restarting PoE via SSH on a USW-Lite-16-PoE

I recently moved my Unifi controller off of my Proliant MicroServer and on to a Raspberry Pi, which is powered via PoE from my main Unifi USW-Lite-16-PoE switch. This evening this Pi was unresponsive, and unlike on the MicroServer there is no out-of-band interface I could use to restart it. If this did not host the Unifi controller I could have used the controller to power-cycle the PoE port, but as the controller couldn’t be accessed either I needed another approach. While I could have just got up and went under the stairs to pull some cables, it would be preferable to be able to solve this via SSH.

There are many posts on the Unifi community forums with solutions for this involving telnet after connecting to the switch via SSH, but telnet is not available on the newer devices like the USW-Lite-16-PoE.

I came across this reddit post which pointed me in the direction of the swctrl poe command.

To list the PoE status of the ports on this device that support PoE:

NetworkRack-USW-Lite-16-US.6.2.5# swctrl poe show id 1-8
Total Power Limit(mW): 45000

Port  OpMode      HpMode    PwrLimit   Class   PoEPwr  PwrGood  Power(W)  Voltage(V)  Current(mA)
----  ------  ------------  --------  -------  ------  -------  --------  ----------  -----------
   1    Auto        Dot3at     32000  Class 2      On     Good      1.38       53.24        26.00
   2    Auto        Dot3at     32000  Unknown     Off      Bad      0.00        0.00         0.00
   3    Auto        Dot3at     32000  Class 4      On     Good      3.40       53.11        64.00
   4    Auto        Dot3at     32000  Unknown     Off      Bad      0.00        0.00         0.00
   5    Auto        Dot3at     32000  Unknown     Off      Bad      0.00        0.00         0.00
   6    Auto        Dot3at     32000  Class 4      On     Good      6.81       53.24       128.00
   7    Auto        Dot3at     32000  Unknown     Off      Bad      0.00        0.00         0.00
   8    Auto        Dot3at     32000  Class 3      On     Good      4.63       53.24        87.00

This doesn’t include any of the port labels, but at a guess the highest current draw is likely the Pi that has hung.

This port can be turned off by running swctrl poe set off id 6, then switched back on with swctrl poe set auto id 6.

As a word of caution with this though - originally I had ran swctrl poe set off 6 (note the missing id between off and 6). This is the incorrect syntax, so it ignores the number and turned PoE off on all ports of the switch. This was a problem for me as the Wifi Access Points were also powered by this switch so I needed to go reconnect with a cable to re-enable PoE for the access points too.

A safer option, sent in by Shawn Kelley, is the restart command. So instead of setting poe “off” then “on” you can run swctrl poe restart id 6 to power cycle the port.