Troubleshooting Tip: False positive redundant power supply failure log on FortiGate 20xE/10xE

There are a few FortiGate models, such as the FortiGate_10xE/FortiGate_20xE, which do not include a Redundant Power Supply (RPS).

After installing FortiOS v7.2.9 or v7.4.3 or above in the FortiGate models FortiGate_10xE/FortiGate_20xE, the following System Event log will be generated:

date="2025-06-24" time="13:44:34" devid="xxxx" vd="root" type="event" subtype="system" action="ipmc-sensor-monitor" bid=58969441 devname="FG200E-1" dstepid=3 dsteuid=3 dvid=1497 epid=3 euid=3 eventtime=1750765474000 id=7516994200315923187 level="information" logdesc="Optional power supply not detected" logid="0100022106" logver=700120523 msg="Power Supply is not detected: PSU RPS LOST" status="anomaly" tz="+0200"

Running the command 'execute sensor list' or 'execute sensor detail' on these FortiGates, it prompts the following output:

FG200E# execute sensor list
[HW monitor sensors]
1 FAN 1 CPU Fan Speed .......... 4299 RPM
2 FAN 2 CPU Fan Speed .......... 4687 RPM
3 FAN 3 REAR FAN ............... 4470 RPM
4 TMP 1 Thermal sensor 1 ....... 29.0 C
5 TMP 2 Thermal sensor 2 ....... 31.0 C
6 TMP 3 Thermal sensor 3 ....... 31.0 C
7 PSU MAIN ...................... OK
8 PSU RPS ....................... LOST

FG200E# execute sensor detail
[HW monitor sensors]
1 PSU MAIN ...................... OK
Type : PSU status (10/0)
Sensor status : Normal
Alarm : No
Value : 1.00
2 PSU RPS ....................... LOST
Type : PSU status (10/0)
Sensor status : Normal
Alarm : Yes
Value : 0.00

The output shows that the PSU RPS is lost from the device, but, in reality, there is no PSU RPS available for this model.

Debugging the IPMC Monitor will show the following information:

FG200E# diagnose debug application ipmc -1
Debug messages will be on for 30 minutes.
FG200E# diagnose debug enable

FG200E# hw_monitor_read_sensor_value()-691: 'PSU MAIN' sensor value is {+1.00}
hw_monitor_read_sensor_value()-691: 'PSU RPS' sensor value is {+0.00}

The value of the 'PSU_RPS' is zero.

When using a Network Monitoring System (NMS) to poll information from the FortiGate, a critical alert will be generated as a consequence of that. This alert is a false positive, and there is no reason to be concerned when using FortiGate 10xE/20xE.

To bypass the issue, it is necessary to:

1. Manually clear the log from the NMS system.
2. Roll back to a working FortiOS version.

Contact TAC support if more information is needed.