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Official bootable images (e.g., Bootable_UCSInstall_UCOS_12.5.1.10000-22.sgn.iso ) are generally not available for direct public download from the standard Cisco Software Download page. Instead, they are obtained through:
If you can only download the upgrade ISO (non-bootable) from Cisco's support site, you can technically convert it into a bootable image for lab use using tools like or Linux commands:
Re-inject the boot file into the ISO and save it as a new file. This modified ISO can now be used to boot a Virtual Machine in ESXi. Installation Requirements for CUCM 12.5
Open the non-bootable ISO and locate the isolinux folder. Extract the isolinux.bin file.
This portal (which replaced the Product Upgrade Tool - PUT) allows users with active subscriptions to order eDelivery links for full install and upgrade media.
Use a tool like UltraISO to load the ISO and select "Generate Boot Info Table" under the bootable tab.
For customers who have already purchased the software but need to re-download the installation media.
Once you have the bootable ISO, ensure your environment meets these minimums: Cisco Unified Communications Manager Version 12.5
