Hi, CML Server is based on Openstack, CML Client is based on Java.
These are the supported versions of ESXI.
• Release 5.1 U2 (Build 1483097) with VMware ESXi
• Release 5.5 U1 (Build 1623387) with VMware ESXi
• Release 6.0 (Build 2494585) with VMware ESXi
For further details you can refer the installation guides in the below link
http://www.cisco.com/c/en/us/support/cloud-systems-management/modeling-labs/products-installation-guides-list.html
Thanks.