"Online" alerts occur anytime a device makes connection to NetCloud Manager.
"Offline" alerts occur anytime a device loses connection to NetCloud Manager. NetCloud Manager has a regular connection process that ensures connectivity to the device while reducing the management plane traffic. If the connection to the device is lost, the device is reported offline and the Offline alert is generated. Typically, the alert is sent within 120 seconds of the device going offline but can take as long and 180 seconds on rare occasions. A device can go offline and come back online without an alert being generated, for example due to the very brief loss of a WAN connection.
Note
Reboot alerts occur when a device is rebooted. Reboot alerts can be accompanied by an Online alert to indicate that a reboot of the device has completed.