Cisco Nexus 5020’s Power Sequencer Methodology

My observations of the not-so-widely known power sequencer issue with Nexus 5020 Switches and the power sequencer issue required prior to the upgrading of these switches.

A quick segway if you’ll allow:

ALWAYS run the “show install all impact kickstart bootflash:n5000-uk9-kickstart.5.0.2.N1.1.bin system bootflash:n5000-uk9.5.0.2.N1.1.bin” command before you begin your code version upgrade. Some Nexus switches have experienced the following error during this validation:

“Extracting "system" version from image bootflash:/n5000-uk9.5.0.2.N1.1.bin.

[# ] 0%[# ] 0% -- FAIL. Return code 0x404F0003 (SRG file not present/cannot be opened).

Version Compatibility check failed. Return code 0x40930012 (SRG extraction failed).”

The resolution to this issue is to reboot the switch and re run the above command run a second time to successful completion.


I recently received a replacement 5020 from Cisco’s RMA depot recently and received it with the following code nx-os 4.0(1a)N2(1a). When I upgraded the code to 4.1(3)N1(1), I performed the ‘show version’ command, and yet no power sequencer version appeared. At present, outside of a show version & the above “show install all impact…” command there’s no other way that I’m aware of to ascertain what version the power sequencer is actually using. Post upgrade to Nexus 4.1(3)N1(1) code, the switch auto rebooted as explicitly identified in the output of the script. Presently the bios is at 1.2 and this means that there won't be the requirement of a bios upgrade. However, when upgrading to the nx-os 5.0(2)N1.1 code, the switch doesn't show the power sequencer code level yet. At the end of the installation from 4.1(3)N1(1) to 5.0.2.N1(1) the switch performed an expected auto reboot. While the reload is taking place, the power sequencer version is still an unknown value. Post successful reboot the code version is now at 5.0.2 and the power sequencer is now running at version 1.0.

Post install of the 5.0(2)N1.1 code, run the “sh install all impact kickstart bootflash:n5000-uk9-kickstart.5.0.2.N1.1.bin system bootflash:n5000-uk9.5.0.2.N1.1.bin”command again. The resulting effort will identify that the power sequencer version will climb to version 1.2.

Upon completion of thesecondary installation of the 5.0(2)N1(1) code, the screen will display the following below:

“Module 1: Refreshing compact flash and upgrading bios/loader/bootrom/power-seq.

Warning: please do not remove or power off the module at this time.

Note: Power-seq upgrade needs a power-cycle to take into effect.

On success of power-seq upgrade, SWITCH OFF THE POWER to the system and then, power it up.

Note: Micro-controller upgrade needs a power-cycle to take into effect.

On success of micro-controller upgrade, SWITCH OFF THE POWER to the system and then, power it up”

The result will state below

“100% -- SUCCESS”


STOP! Start your stopwatches for FIVE minutes, the install process has NOT completed even though the above states 100% success. It is during this window that the power sequencer still reports the version as v1.0.

At the five minute mark of the switch sitting idle, the switch will post to the screen

“Install has been successful.”//It is at this moment that the power sequencer changes to version 1.2.

Please run a “show version” command at the prompt to validate the information above.

This is the very first time that you can actually power down the Nexus 5K switch via power cycle (not reload) & expect the switch to return to productivity.

During the switch’s upgrade from 5.0(2)N1(1) to 5.0(3)N2(1) there wasn't any reboot required. The power sequencer was at version 1.2 and the bios incremented to version 1.3. If you’re like me, you have an established outage window. Reboot the switch instead of opting for the ISSU. You won’t regret it and you’ll have properly booted off of the new code that you’ve upgraded on your Nexus 5K.

In closing, the focus isn’t necessarily on the version of code that you upgrade to so much as it’s the observation & the importance of the power sequencer’s version via the “show impact all” command” and the “show version” command.


When upgrading thenx-os code on a Nexus switch have an additional laptop plugged into the console to log any and all changes for additional information & validation.