CUCM 12.5 dropped support for legacy M3 series UCS servers. Attempting to boot the ISO on unsupported hardware will show a red fatal error. Check the for 12.5 before downloading.
If you cannot find the bootable image in your portal, you can contact Cisco Licensing Support to request a "Software Delivery" link for the bootable version of your licensed software. cucm 12.5 bootable iso download
Cisco does not allow public distribution of its Unified Communications Manager software. Unlike Linux ISOs (Ubuntu, CentOS) or open-source tools, CUCM is commercial, licensed software requiring a valid support contract. CUCM 12
To obtain the legitimate CUCM 12.5(1)SU3 (or similar) bootable ISO, the following steps are required: If you cannot find the bootable image in
: You must deploy the correct CUCM 12.5 OVA template before mounting the ISO. This sets up the necessary CPU, RAM, and disk reservations.