The UNKNOWN service status is displayed in grey throughout the up.time user interface.  A service will enter an UNKNOWN state under any of the following conditions:

• The host that the service resides on has gone offline.
• The host on which the service resides has entered a scheduled maintenance or downtime period.
• The service monitor could not be executed by the monitoring station.

Any time the status of the monitor can not be directly verified, the monitor will enter the UNKNOWN state.