PRTG System Health sensor reported as down in Cisco switches

After a PRTG upgrade I noticed that the PRTG System Health sensor reported as down in Cisco switches all of the sudden, the sensors System Health for "Currents", "Other" and "Voltages" of your PRTG system are all down and in red... what's is going? A power spike? Have all switches failed at once? How is that possible?


Nothing to worry about... for the moment. The issue is caused by a "glitch" in PRTG, losing the measurements units for some of the channels of the sensor, and hence reporting astronomical values for these sensors, because the values no longer have decimal points for example.

Verify this is the case by visiting the "Overview" tab of any of the faulty sensors, and checking the Channels section, is any of them missing the unit values? let's say mA (milliamperes), dBm (decibel-miliwatts) or V (voltage)?


If some of them have got it missing, edit the relevant channel and add the value in the unit field, in the screenshot below I'm adding the missing "V":

Still within the affected channel, scroll a bit down and ensure the Value Lookups and Limits is set to "Enable alerting based on value lookups", and to a value lookup of None, this will ensure that channel is not messing with the sensor by reporting huge values up or down

Do the same thing for the other sensors with missing faulty channels, setting their units and enabling lookup values



Thank you for reading! And I hope that this article helps you


London, 28 December 2019



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