When you add an ESX host to vCenter using either its FQDN or its short host name, the hosts file on vCenter is queried. By default the hosts file is located in %SystemRoot%\system32\drivers\etc\hosts.
If the FQDN is the first entry in the hosts file after the IP address, the FQDN displays in vCenter for the ESX host. If the short host name is the first entry in the hosts file after the IP address, then the short host name displays in vCenter.
To display the FQDN, ensure it is listed first in the hosts file. For example:
192.168.0.5 esx-server-1.domain.com esx-server-1
To display the short host name, ensure it is listed first in the hosts file. For example:
192.168.0.5 esx-server-1 esx-server-1.domain.com
Based on VMware KB 1005750