What is this?

This knowledgebase contains questions and answers about PRTG Network Monitor and network monitoring in general.

Learn more

PRTG Network Monitor

Intuitive to Use. Easy to manage.
More than 500,000 users rely on Paessler PRTG every day. Find out how you can reduce cost, increase QoS and ease planning, as well.

Free Download

Top Tags

View all Tags

New Alerts on Service Restarts



Dear Support Team,
Suppose I currently have 200 down sensors in the PRTG. The downtime of these is 100 days. When the service restarts (sometimes manually, sometimes due to system overload or other problems), some of them are shown in "New Alerts" and PRTG says: The sensor is down for 1 hour!!! While this sensor has been down since 100 days ago!
Please tell, why does this happen? And why does this not happen for all down sensors?!!
I would also add that I'm not sure this happens when the system restarts manually or when it restarts due to a problem.
Thank you

alerts down down-sensors downtime new-alerts service-restart

Created on Apr 27, 2021 12:44:47 PM

1 Reply




Depending on how long the restart takes, a restart of PRTG might reset sensor states since these states are not saved in the PRTG configuration file, instead they are cached. During the restart, all caches are deleted and so the states are also reset. This behavior cannot be changed. Therefore the Notification will be send again as well. This is also to ensure you don't miss any new alarms during the downtime of PRTG.

Created on Apr 28, 2021 1:53:42 PM by  Timo Dambach [Paessler Support]

Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.