This article describes the reason behind the alarm and the steps to determine whether this is a false positive or if this is a true alarm.

You will see the following alarm on the device however the fans seem t be running okay without any issues.

user@QFXD> show chassis alarms no-forwarding

2 alarms currently active

Alarm time              Class Description

2023-05-23 19:05:37 UTC Minor FPC0: Fan Tray 3 Fan 1 Spinning Upgraded

2023-05-23 18:59:21 UTC Minor FPC0: Fan Tray 2 Fan 1 Spinning Upgraded

The alarms of “Fan Tray X Fan Y Spinning Upgraded” and “Fan Tray X Fan Y Spinning Degraded,” which were introduced in newer codes, merely tell whether the current fan speed in RPM is within the tolerance level (+/- 30%) of the corresponding Fan speed level. So, if the fan speed level is normal (because the temperature is normal), the fan speed is supposed to be +/- 30% of 6000 for fan-0 and +/- 30% of 5300 for fan-1 (These threshold values are in reference to a QFX5200 device. Please check the hardware documentation for device-specific RPM values). If, for instance, the fan speed decreases below 3710 or increases above 6890 in the above scenario for fan 1, these minor alarms will appear. 

We have to note that the threshold values for fan0 and fan1 are different. This was a bug where these RPM values for Fan tray 0 and 1 were mismatched, and they needed to be the same for proper performance.

Moreover, if the temperature becomes slightly high and fans start to spin at intermediate speed (around 9000 RPM), and at this fan speed level the fan speed is within +/- 30% of 9000 RPM, there will be no alarm.

Due to the above-stated facts, these alarms don’t represent any useful or actionable information and are best ignored. However, by checking and comparing the following outputs, you will be able to determine if this alarm is true or if it is a false positive.

user@QFXD> show chassis environment no-forwarding

Class Item                          Status    Measurement

Fans FPC 0 Fan Tray 0 Fan 0        OK        Spinning at normal speed

     FPC 0 Fan Tray 0 Fan 1        OK        Spinning at normal speed

     FPC 0 Fan Tray 1 Fan 0        OK        Spinning at normal speed

     FPC 0 Fan Tray 1 Fan 1        OK        Spinning at normal speed

     FPC 0 Fan Tray 2 Fan 0        OK        Spinning at normal speed

     FPC 0 Fan Tray 2 Fan 1        OK        Spinning at normal speed

     FPC 0 Fan Tray 3 Fan 0        OK        Spinning at normal speed

     FPC 0 Fan Tray 3 Fan 1        OK        Spinning at normal speed

     FPC 0 Fan Tray 4 Fan 0        OK        Spinning at normal speed

user@QFXD> show chassis fan

   Item            Status  RPM   Measurement

   FPC 0 Fan Tray 0 Fan 0  OK    5908  Spinning at normal speed

   FPC 0 Fan Tray 0 Fan 1  OK    6482  Spinning at normal speed

   FPC 0 Fan Tray 1 Fan 0  OK    5875  Spinning at normal speed

   FPC 0 Fan Tray 1 Fan 1  OK    6467  Spinning at normal speed

   FPC 0 Fan Tray 2 Fan 0  OK    6250  Spinning at normal speed

   FPC 0 Fan Tray 2 Fan 1  OK    6870  Spinning at normal speed

   FPC 0 Fan Tray 3 Fan 0  OK    6157  Spinning at normal speed

   FPC 0 Fan Tray 3 Fan 1  OK    6844  Spinning at normal speed

   FPC 0 Fan Tray 4 Fan 0  OK    5960  Spinning at normal speed

   FPC 0 Fan Tray 4 Fan 1  OK    6666  Spinning at normal speed

In this scenario, we can see that the fans are spinning at normal speed and RPM values are within the desired range, and hence this is a false positive. These alarms, if they appear, don’t clear on their own. Meaning that once they appear due to the fan speed reaching slightly elevated or low levels, they will not clear even when the fan speed becomes completely normal. The behaviour was introduced in Junos:21.3R1 junos:21.4R1 and is resolved in the following release junos:21.4R3-S5 junos:22.1R3-S4 junos:22.2R3-S2 junos:22.2R3-S3 junos:22.3R3-S1 junos:22.4R3 junos:23.1R2 junos:23.2R2 junos:23.3R1 junos:23.4R1 junos:23.4R2 

This issue is tracked under PR: https://prsearch.juniper.net/problemreport/PR1738865 

You may also refer to the overview documentation for your specific device and compare the RPM and double-check if the speed falls within normal ranges. In case it is beyond the limits, please open a JTAC case for further assistance. 

2023-05-31- Initial Publication
2024-01-24 - Added additional details to the KB and formatting done
2025-07-31 - Updated the releases that have the fix for this issue.

2026-07-21 - evalle - Added the correct PR1738865 and grammar improvment. Previous incorrect PR1700957 removed.