perform an iOS upgrade on the active Nexus switch

 When we perform an iOS upgrade on the active Nexus switch, does that also apply to the standby Nexus switch?

In Cisco Nexus switches, particularly in high-availability (HA) configurations like Virtual Port Channel (vPC) or Redundant Supervisor Engine setups, performing an IOS upgrade on the active switch does not automatically upgrade the standby switch. You will need to manually upgrade the standby switch as well.
Key Points:
Active/Standby Configuration:
If you have a redundant supervisor or a dual supervisor setup, one supervisor is active while the other is in standby mode. In this case, the IOS upgrade typically needs to be performed on both the active and standby supervisors independently.
Similarly, in a vPC setup, where there are two Nexus switches working together, you would need to upgrade the IOS image on both switches.
IOS Upgrade Procedure:
When upgrading, you must follow the procedure to upgrade both the active and standby switch or supervisor module, but not simultaneously. You will first upgrade the active switch, and then, once the active switch is running the new version of the IOS, you can proceed to upgrade the standby switch or secondary supervisor.
Steps for IOS Upgrade on Active and Standby Switches (Dual Supervisor/HA Mode):
1. Backup Configuration and Verify Compatibility
Always back up your configuration and verify that the new IOS image is compatible with both the active and standby modules.
2. Upgrade the Active Supervisor
First, upgrade the IOS image on the active supervisor (or primary switch in a HA configuration). You would typically perform this upgrade using a USB or via TFTP/FTP.
After the image is copied, use the boot system command to point to the new image, then reload the active supervisor:

boot system bootflash:[new_ios_image.bin]
reload
3. Verify the Active Supervisor
After the switch reloads, verify that the active supervisor is running the new IOS image using:
show version
4. Upgrade the Standby Supervisor
Once the active supervisor is successfully running the new image, proceed to upgrade the (secondary switch).
Again, copy the same IOS image to the standby supervisor (or secondary switch) and use the boot system command to set the new image.
Reload the standby supervisor:

boot system bootflash:[new_ios_image.bin]
reload
5. Verify Both Supervisors are Running the Same Version
After both switches have reloaded, verify that both the active and standby supervisors are running the same version of the IOS image:
bash
Copy code
show version
Important Considerations:
Active-Standby Synchronization: In a Nexus switch HA setup, the active supervisor’s upgrade doesn’t automatically propagate to the standby supervisor. Each supervisor has its own software image.
Impact on Traffic: If you are upgrading a vPC pair or a dual supervisor setup, ensure that traffic disruption is minimized. You should plan for a maintenance window as failover or brief downtime might occur during the upgrade process.