Can someone please advise if it is necessary to upgrade IP end points (Cisco phones and VG gateways) to the specific device defaults based on the CUCM version or OK to leave them as it is if they are already on a minimum recommended version? Got a customer with 8K endpoints and don't want to disturb their existing setup, but looking to CUCM upgrade from Version 11.5 to 12.5. Their phones already on the minimum recommended version. Thanks
I would recommend that you review the ReadMe Notes of the CUCM version you are upgrading to (available in the download details section of the SU). Those notes will include the firmware versions that will be installed during the upgrade. Your end points should be running those versions prior to the CUCM upgrade.
When you upgrade the CUCM version, the phone will upgrade to the firmware version which came with the CUCM 12.5 software . On CUCM readme guide Cisco mentioned the phone firmware included with the version.
I've been upgrading CUCM since version 6 and we always check the firmware version that the upgrade version is having for default. To minimize the time the upgrade takes, because we have 14 servers in our cluster, we upgrade all phones to the latest firmware before the upgrade. Also, make sure you read all of the release notes for caveats and other potential issues.