Is there any reason for many duplicate hosts? If these are cluster servers, the unique IPs should be imported as a Cluster system type in Capacity Planner.
Having duplicate host names would typically not happen in a given single environment or DNS block. Otherwise you would have duplicate host names issues on a network. If you have a production environment and a developmental clone, then assess these blocks separately (company ID and Collector)
The way CP works has been the same for some time, maybe Capacity Planner 2.6 or earlier. See KB 1008160 (http://kb.vmware.com/kb/1008160/)
Best Regards,
Jon Hemming
