PRTG Manual: Sensor States

The color of a sensor or object indicates its status. In the table below, you find a list of states that a sensor or object can show. This list also reflects the priority of the sensor states whenever PRTG shows summarized sensor states, for example, in the device tree or in geographical maps. For example, if all sensors on a device show the Up status and one of the sensors changes to the Down status, the device shows the Down status as well because this status has a higher priority. The device is then displayed accordingly in the extended device tree views.

The Down and Down (Partial) states are considered to be equal regarding status priority.

In the device tree, hover over an object's name to view the total number of alarms for the object. In geographical maps, hover over over the location marker to view the total number of alarms at this location.

Status Icon	Status Name	Meaning
/	Down	At least one sensor on this object (or at this location) shows the Down status. PRTG is unable to reach the device or the sensor has detected an error. For more information, see section Sensor Behavior for the Warning and Down States. In this case, the sensor does not record any data in its channels while it shows the Down status. There is an error limit in the channel settings or the sensor shows the Down status because of a lookup. In this case, the sensor continues to record data in all channels although it shows the Down status.
	Down (Partial)	In a cluster, at least one cluster node reports that this sensor shows the Down status, while at least one other cluster node reports that the same sensor shows the Up status. This status is not available for sensors on remote probes in a failover cluster.
/	Down (Acknowledged)	At least one sensor on this object (or at this location) showed the Down status and a user acknowledged this status via Acknowledge Alarm in the context menu. There is no sensor in the Down status. For acknowledged alarms, PRTG does not send further notifications. If you pause and resume a sensor in the Down (Acknowledged) status, it shows the Down status again.
/	Warning	At least one sensor on this object (or at this location) shows the Warning status. The sensor detected an error and shows the Warning status but the sensor is trying to reach the target device again. The sensor might soon change to the Down status. For more information, see Sensor Behavior for the Warning and Down States. There is a warning limit in the channel settings or the sensor shows the Warning status because of a lookup. There is no sensor in the Down or Down (Acknowledged) status.
/	Unusual	At least one sensor on this object (or at this location) shows the Unusual status. The sensor reports unusual values for this weekday and this time of the day. The unusual detection is based on the sensor's historic average data. You can configure or disable the unusual detection in the system administration settings under Monitoring. You can also disable the unusual detection for specific groups. For more information, see section Group Settings. There is no sensor in the Down, Down (Acknowledged), or Warning status.
/	Up	All sensors on this object (or at this location) show the Up status. The last scan was okay and the sensors receive data. There is no sensor in the Down, Down (Acknowledged), Warning, Paused, or Unusual status.
/	Paused	All sensors on this object (or at this location) show the Paused status. The sensor is paused for a specific time span, indefinitely, or because of a dependency. There is no sensor in the Down, Down (Acknowledged), Warning, Unusual, or Up status. A sensor in the Paused status does not count towards the maximum number of sensors that your license allows.
/	Unknown	All sensors on this object (or at this location) show the Unknown status. The sensor has not received any data yet or there is an error in (network) communication, likely on the probe system. If sensors continuously show this status, you might need to restart PRTG. For more information about extended troubleshooting, see the Knowledge Base: What to check if sensors are gray? and My sensors show the Unknown status after a PRTG core server restart. What can I do? There is no sensor in the Down, Down (Acknowledged), Warning, Unusual, Paused, or Up status.

Sensor Behavior for the Warning and Down States

The Down status indicates that there is an issue with an object, for example, a device. There are various reasons for the Down status, for example, an interruption in the physical connection to the device or an internet connection outage.

After a failed request, PRTG tries to contact the device again before it sets a sensor to the Down status (this is true for almost all sensors):

If a request to a device fails for the first time, the sensor changes to the Warning status. PRTG repeats the request and immediately attempts to rescan the device.
If the second request also fails, the sensor changes to the Down status by default until the device is reachable again. You can change this behavior in the scanning interval settings of any object in the device tree. PRTG tries to reach the device with every scanning interval.

This procedure gives devices and services the chance to recover from a momentary overload and prevents false alarms. Still, you are immediately informed about any network issues.

This behavior does not apply to the Warning or Down states that result from warning limits or error limits in the channel settings. This behavior also does not apply to channels that use lookups.