Passive monitors are the WhatsUp Gold feature responsible for listening for device events. As active monitors actively query or poll devices for data, passive monitors passively listen for device events. Because passive monitors do not poll devices on a regular basis, they use less network bandwidth than active monitors.
Passive monitors are useful because they gather information that goes beyond simple Up or Down service and device states by listening for a variety of events. For example, if you want to know when someone with improper credentials tries to access one of your SNMP-enabled devices, you can assign the default Authentication Failure passive monitor. The monitor listens for an authentication failure trap on the SNMP device, and logs these events to the SNMP Trap Log. If you assign an action to the monitor, every time the authentication failure trap is received, you are notified as soon as it happens.
Although passive monitors are useful, you should not rely on them solely to monitor a device or service--passive monitors are meant to be used in conjunction with active monitors. When used together, active and passive monitors make-up a powerful and crucial component of 360-degree network management.
Creating a successful passive monitor requires that you take several steps:
Important: Before you attempt to create a passive monitor, you should know the specific traps (and coinciding MIBs) for which you want WhatsUp Gold to listen --this will make the process much easier for you.
Additionally, after you create a passive monitor, you can configure alerts to notify you when a particular trap is received.