News & Events

What’s New In CUCM 15?

  • 16 February, 2024

Article, Cisco, Unified Collaboration

CUCM 15 has arrived!

CUCM 15 was released in December 2023 with 15.1.X being released later this quarter of 2024. Cisco have made significant hardware changes which may surprise many and potentially make it difficult to directly upgrade from 12.5 or even 14.X. Any CSR versions Pre-12.5 will be even more difficult.

We have done our best to outline these changes given the limited time this release has been out. This is the by far the biggest change we have seen in the last 15 years since CUCM 4.X, a Windows based install moved to CUCM 5.X a Linux Redhat install.

In this article, we have summarised some of the required hardware specs, interesting features, and the best approach to tackling this upgrade.

Hardware changes in CUCM 15

Clearly one of the main drives for these significant hardware changes is Cisco have adopted Linux’s move to no longer support CentOS, but rather a 64-bit AlmaLinux Architecture. These changes will have to be made in the system in a shutdown state highlighted below. See more.

  • 80GB vDisk deployments, will have to manually be resized to the HDD size of 110 GB in a VMware’s shutdown state.
  • Existing vRAM allocations on 8GB integrations are not supported, but must be at least 10GB.
  • ESXi 7.0 or 8.0. is only supported due to VMware CentOS EOL dates.
  • vCPU physical CPU requirements are exactly the same as CUCM v14.

What does this mean? A complete rebuild of the PUB from scratch with the appropriate Hardware/OVA Templates? Not at all! Cisco have kindly allowed us to gracefully shut down the VM and modify the vRAM and vDISK accordingly.

Note: Pre-12.5.X Direct upgrades are not supported so the best option is to rebuild your server with a 15.X. fresh install and perform a data Import.

Supported upgrade paths

Note: Any deployments still on the CSR 11.5 Architecture will be EOL May 31st 2024


CUCM 12.5  EOL

Depreciated Phone list (Still the same as 14.X)

General Hardware support list 

Free CUCM 15 Workflow Upgrade Download

New features of CUCM 15

  • CUCM 15.X supports integration with the Webex Control Hub adopting Enhanced Survivability Node (ESN), where the Local CUCM can act as a backup instance for Webex Cloud Calling.
  • CUCM UI supports the display of HVD (Hosted Virtual Desktop ) IP addresses and thin-client IP address for the Webex Calling Infrastructure. This is achieved by viewing the Real-time Device Status section in CUCM.
  • Webex Calling users for MS Teams can view call history for shared devices registered to the CUCM, but must be in a Webex Cloud-Connected UC integration.
  • Auto provisioning support for Webex Teams and Jabber clients for LDAP users synchronized with Microsoft Active Directory.
  • Cluster Software location feature allows the central management of CSR software for all cluster nodes from the Publisher so no more does software need to reside on the individual Cluster nodes. The CLI “utils system upgrade”, “utils system upgrade cluster” commands can utilize this feature.
  • Unified RTMT 15.X installation is now supported on the Windows 11.
  • H.323 Gatekeeper will no longer be supported, it’s recommend to use SIP trunks with Location Bandwidth Manager (LBM)

Read more about these features here.

What about IM&P, CUC (Unity), CER (Emergency Responder) & Expressway 15.X?

IM&P, CUC (Unity) and CER (Emergency Responder) are all based on similar hardware requirements, except Expressway.

VMware ESXi Hardware requirements:




Expressway 15.X (Hardware surprisingly hasn’t changed)

Final note...

Cisco have yet to adopt supporting other cloud offerings i.e. AWS, Azure or GCP but have rather innovated within their own Webex Cloud space making CUCM a natural extension to Cloud calling. The Webex Control Hub even supports YeahLink phones, which has to soon be in the pipeline for CUCM.

Yeah Link Phones support Webex Calling

What about UCCX still on 12.5? No version 14 or 15 yet, we suspect this product is being phased out for Webex Contact Centre, but it’s all speculation at this stage as UCCX’s release dates historically haven’t coincided with CUCM.

If you would like help with your upgrade to CUCM 15, we’d be more than happy to assist. You can find a link to contact us below.

Need Upgrade Help?

Whatever version you are currently on, arrange a quick call with us so we can help you with any of your CUCM 15 upgrade questions.