Symptom

+++ A Nexus 9000 series switch with front-to-back fans installed will increase fan speed to 100% after a minor temperature alarm is triggered. +++ After temperature alarm is cleared and temperatures return to normal values, fan speed will remain at 99-100% of maximum capability: switch# show environment fan detail Fan: --------------------------------------------------------------------------- Fan Model Hw Direction Status --------------------------------------------------------------------------- Fan1(sys_fan1) NXA-FAN-30CFM-B -- front-to-back Ok Fan2(sys_fan2) NXA-FAN-30CFM-B -- front-to-back Ok Fan3(sys_fan3) NXA-FAN-30CFM-B -- front-to-back Ok Fan_in_PS1 -- -- front-to-back Ok Fan_in_PS2 -- none None Fan Zone Speed: Zone 1: 0x80 Fan Air Filter : NotSupported Fan: ------------------------------------------------------------------ Fan Tray Fan Fan Direction Speed(%) Speed(RPM) ------------------------------------------------------------------ Fan1(sys_fan1) fan1 front-to-back 100 16413 Fan1(sys_fan1) fan2 front-to-back 100 11464 Fan2(sys_fan2) fan1 front-to-back 100 16314 Fan2(sys_fan2) fan2 front-to-back 99 11297 Fan3(sys_fan3) fan1 front-to-back 100 15472 Fan3(sys_fan3) fan2 front-to-back 100 11612

Conditions

+++ Nexus 9000 series switch has front-to-back fans installed +++ Minor temperature alarm has been triggered on the device at some point in the past (including during initial boot-up of the device) +++ Fan speeds remain at 99-100% of maximum capacity per the output of `show environment fan detail`, even when temperature sensors indicate temperatures are normal

Workaround

+++ No known workaround at this time

Further Problem Description