On an HP server, when you get this event log message:
Source: Foundation Agents
A ‘Host Health status change’ trap indicates that health status has changed.
Change in health status ‘UNKNOWN’
This can be investigated further by starting up the HP System Dashboard. It does not necessarily mean that there is an issue, typically you get this when rebooting a server and not all aspects of the server are fully connected (such as NICs). This can also be the case when the Foundation Agents report Change in health status ‘FAILED’. Either way, you should investigate this with the dashboard.