Unlike active monitors or performance monitors, which actively poll a device to check its status or to gather statistical data, passive monitors passively listen for events on devices.
Because it does not repeatedly poll devices and wait for a device to signal a problem, a passive monitor uses less resources than an active monitor both on the machine running WhatsUp Gold and on the network.
Passive monitors are also useful because some devices on a network may not provide a clear up or down status when queried. For example, a message may get logged to the system's Event log by another application (such as an antivirus application alerting when a virus is found). Since these messages/events can occur at any time, a Passive Monitor Listener "listens" for them, and notifies WhatsUp Gold when they occur.
However, the information that can be reported into a passive monitor event is not as customizable as it is with active monitors. In the case of a severe device failure, a device may enter a state where it is not able to successfully send a passive monitor event. A connectivity loss may prevent the WhatsUp system from receiving an event sent to it as well.
Passive monitors should be used to complement active monitors, but you should not rely solely on passive monitors to monitor a device or service.
The first step to use this function is to Configure the Passive Monitor Listeners.
After the listeners have been configured, you can Configure Passive Monitors for individual devices.
When a passive monitor is configured on a device, the device icon displays a diamond shape on the upper left side.
This shape changes color when an unacknowledged state change occurs on the monitor. After the device has been acknowledged, the icon returns to the above appearance.