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PRTG Manual: Dependencies
Using dependencies, you can pause sensor monitoring based on the status of another sensor in order to avoid false alarms and incorrect downtime recording. A dependency stops the monitoring of one sensor or a set of sensors as soon as a specific sensor is not in an Up status. This means, for example, you can stop monitoring remote network services when the corresponding firewall is down due to connection problems.
When using the auto-discovery function, the Ping sensor on a device is by default set as the master object for this device. This means that monitoring for the entire device is paused if the Ping sensor is in a Down status. Usually, it does not make sense to monitor other aspects of a device with other sensors while the Ping sensor indicates that the device is not even reachable.
In order to view a list of all dependencies or only selected dependencies, choose Devices | Dependencies and the corresponding dependencies path from the main menu. From there you can also access the Dependencies Graph that visualizes all dependencies within your network.
For more information about the dependency settings, please see the settings of the respective object you want to set a dependency for.