Cisco Cucm 12.5 Virtualization Requirements Work -

| Component | Small (1000 users) | Medium (2500 users) | Large (10000 users) | | :--- | :--- | :--- | :--- | | | 4 | 8 | 8 or 12 | | RAM | 8 GB | 16 GB | 24 GB | | Disk (Thick Provisioned) | 160 GB | 300 GB | 300 GB+ | | Network Adapter | VMXNET3 (1 or 2 interfaces) | VMXNET3 | VMXNET3 |

If migrating from CUCM 10.5 or 11.5 to 12.5, note that the virtualization requirements have tightened:

CUCM 12.5 VMs are extremely sensitive to packet loss and out-of-order delivery. The virtual network must mirror physical TDM quality. cisco cucm 12.5 virtualization requirements

Database replication fails within hours. Fix: Re-deploy on RAID 10 LUN.

| Hypervisor | Minimum Supported Version | Key Notes | | :--- | :--- | :--- | | | 6.7, 7.0, 8.0 | The only fully supported hypervisor for production. | | Cisco HyperFlex | 3.0, 4.0 | Supported when using ESXi as the underlying hypervisor. | | Nutanix AHV | Limited support | Only for specific partner-managed solutions; not general purpose. | | Microsoft Hyper-V | Not supported | Use only for demo/lab, not production. | | KVM / Proxmox | Not supported | No support; TAC will reject. | | Component | Small (1000 users) | Medium

%RDY time in esxtop exceeds 5%. Calls drop. Fix: Enable CPU reservations and leave 1–2 physical cores idle for hypervisor overhead.

250 GB thin provisioned (thick provision eager zeroed recommended). Fix: Re-deploy on RAID 10 LUN

The hardware requirements for CUCM 12.5 virtualization vary depending on the chosen platform. Here are some general guidelines:

Cisco Unified Communications Manager (CUCM) 12.5 requires a virtualized environment, as it cannot be installed directly on bare-metal server hardware. Deploying CUCM 12.5 requires specific VMware ESXi versions, Open Virtual Archive (OVA) templates, and precise hardware resource reservations to ensure real-time voice processing performance. Virtualization Software Requirements

Even a genuine Cisco UCS server with the wrong processor family (e.g., using an Intel Xeon E5-2600 v3 when v4 is required) will fail validation. Always cross-reference your exact CPU model with the CUCM 12.5 HCL.

: Must be kept up to date; Cisco recommends checking and upgrading VMware Tools before each power-on. VM Configuration (OVA) Highlights