By default (unless overridden with the uniqueHostId system property), the Agent determines the host name of the OS it is running in using reverse DNS lookup. In some circumstances, this host name may be set as the fully qualified domain name of the host name. If this property is set to true, the Agent removes any domain name and uses the simple hostname to identify the host. In cases where the host name is an IP address (which happens if the DNS lookup fails) then the full IP address in string form is used. The host name is used in mapping metrics gathered by the Machine Agent to application nodes. See Unique Host ID Property.