Studying for the Cisco voice certifications it was needed to have a lab environment with CUCM, Cisco Unified Communication Manager. CUCM is only approved to run in lab environments on VMWare, but with my Xen cluster already in place, with 2 nodes each with 8GB of RAM, that was where I wanted to run it. Plus, it was also a challenge to get it working. This article will describe how to get CUCM running on Xen by first installing it in VMware and then transferring it to Xen.