Basics: IP Phone Firmware & CUCM Upgrades


Within the Collaboration practice here at NetCraftsmen, we always emphasize proper planning as being a major key to the success we’ve had on various projects over the years.  CUCM upgrades are a prime example as there are a number of things to consider before getting started…you may have to look at hardware compatibility, version dependencies with other UC applications, change windows, end user communications…you name it.  One thing that is often overlooked is that firmware revisions can and often do change between versions of CUCM (major or minor).  In some cases, it might be OK to just let the firmware upgrade coincide with the CUCM upgrade.  In others, you may want to avoid being the engineer that accidentally upgraded (or downgraded) all of the phones during a CUCM upgrade.  In either case, you can (and should) plan accordingly and here are some basic considerations:

  • The ReadMe file and/or Release Notes for each CUCM release typically contains a listing of the default firmware revisions included with the software.   In other words, this is what the Device Defaults will be set to in the upgraded release.
  • You should compare the firmware revisions in the upgraded release to the existing device defaults.  Often you will find that the CUCM upgrade will introduce updated firmware revisions; however, it is also possible that you are running a later release than what is specified as the default in the CUCM upgrade for a specific device type.  Focus on the device types applicable to your environment and note all applicable changes.
  • If you’d prefer to continue using the existing firmware, you’ll need to verify compatibility with the CUCM upgrade release.  If the existing firmware version is compatible with the CUCM upgrade release then you’ll need to modify the device defaults as part of the upgrade process.  The same consideration goes for situations where you may be running a later release than what is specified as the default in the CUCM upgrade.

Note:  Instead of modifying device defaults, another option is to use BAT to hardcode desired firmware revisions on the phones

  • If you’d like to go ahead and upgrade the firmware to the default revisions in the CUCM upgrade, then you should check the applicable release notes for each new firmware version.  If you are running outdated firmware, you may find that you cannot directly upgrade to the target release.
  • In some cases, you want to upgrade to a later release than what is specified as the default in the CUCM upgrade (e.g., you find there is a bug in the default firmware revision that you’d like to avoid).  Again, you’ll need to modify the device defaults as part of the upgrade process (or use BAT – see above).
  • Whenever possible, I recommend scheduling firmware upgrades in advance of a CUCM upgrade.  This isn’t always possible but is generally my preference (particularly in larger environments).


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Nick Kelly

Cybersecurity Engineer, Cisco

Nick has over 20 years of experience in Security Operations and Security Sales. He is an avid student of cybersecurity and regularly engages with the Infosec community at events like BSides, RVASec, Derbycon and more. The son of an FBI forensics director, Nick holds a B.S. in Criminal Justice and is one of Cisco’s Fire Jumper Elite members. When he’s not working, he writes cyberpunk and punches aliens on his Playstation.


Virgilio “BONG” dela Cruz Jr.

CCDP, CCNA V, CCNP, Cisco IPS Express Security for AM/EE
Field Solutions Architect, Tech Data

Virgilio “Bong” has sixteen years of professional experience in IT industry from academe, technical and customer support, pre-sales, post sales, project management, training and enablement. He has worked in Cisco Technical Assistance Center (TAC) as a member of the WAN and LAN Switching team. Bong now works for Tech Data as the Field Solutions Architect with a focus on Cisco Security and holds a few Cisco certifications including Fire Jumper Elite.


John Cavanaugh

CCIE #1066, CCDE #20070002, CCAr
Chief Technology Officer, Practice Lead Security Services, NetCraftsmen

John is our CTO and the practice lead for a talented team of consultants focused on designing and delivering scalable and secure infrastructure solutions to customers across multiple industry verticals and technologies. Previously he has held several positions including Executive Director/Chief Architect for Global Network Services at JPMorgan Chase. In that capacity, he led a team managing network architecture and services.  Prior to his role at JPMorgan Chase, John was a Distinguished Engineer at Cisco working across a number of verticals including Higher Education, Finance, Retail, Government, and Health Care.

He is an expert in working with groups to identify business needs, and align technology strategies to enable business strategies, building in agility and scalability to allow for future changes. John is experienced in the architecture and design of highly available, secure, network infrastructure and data centers, and has worked on projects worldwide. He has worked in both the business and regulatory environments for the design and deployment of complex IT infrastructures.