In the "Search Downloads" box, type "Unified Communications Manager (CUCM)" (do not just type "Call Manager"—the algorithm prefers the full name).

For a fresh install, select the (e.g., UCSInstall_UCOS_12.5.1.11900-26.sgn.iso ). Be prepared for large file sizes (4GB to 6GB). Step 3: Understanding the Licensing Model (Switch to Smart Licensing) Downloading the binary is useless without licensing. CUCM 12.5 no longer uses the traditional "Device License Unit (DLU)" system you may remember from versions 10.x.

| File Type | Extension | Purpose | | :--- | :--- | :--- | | | .iso | Full installation media for bare metal or new VMs. | | OS Update | .iso (smaller) | Upgrading from CUCM 11.x or 12.0 to 12.5. | | COP File | .cop.sgn | Patch or upgrade file applied to an existing 12.5 installation. |