When you finally have the legitimate ISO:
If you cannot get access to the official ISO through a Cisco contract, consider these legitimate alternatives: cucm 12.5 bootable iso download
Before you proceed with the installation or upgrade, ensure that your server meets the minimum system requirements for CUCM 12.5: When you finally have the legitimate ISO: If
: Mount the non-bootable ISO and copy its files to a temporary directory. cucm 12.5 bootable iso download