Changes made to your DNS name will propagate into the system within the next 24 hours. Don't expect to see the change immediately.
The DNS lookup will default to examining the "ST.HMC.Edu" domain if only a hostname is entered. If a fully qualified name (such as www.microsoft.com) is entered, then that host will be looked up. This lookup can also do "reverse" lookups, that is you may type in an IP ADDRESS and the lookup should return the current name.