Upgrade an Active-Standby Cluster

In this example we need to upgrade the F5 BIG-IP from 16.1.x to the actual version 16.1.3.5 (7.8.2023).

Download Software Image

Login to https://my.f5.com, search and download the ISO image of the version you want to upgrade:

Select the release and download the ISO:

Create System Archive (Config Backup)

On both nodes create a archive of the config and download it to your PC before upgrading.

You can do this using the WebUI (Or use the tmsh command line) browse to System - Archives and press Create button.

Reactivate License

Maybe your license needs to be reactivated to be able to do the upgrade. This process is described here:
K7727: License activation may be required before a software upgrade for BIG-IP

Use the tmsh command to see the license check date:

tmsh show sys license | grep "Service Check Date"

Reference the License Check Date table listed previously in the link above, and verify that the service check date is a later date than the license check date listed for the version to which you are upgrading.