Network Performance Monitor passive monitors are responsible for listening for device events. As active monitors actively query or poll devices for data, passive monitors simply listen for device events. Because passive monitors do not poll devices, 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 should 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.

In an effort to help you manage your network after you install the application, Network Performance Monitor includes the following pre-configured (default) passive monitors:

  • SNMP Trap Listener
  • Syslog Trap Listener
  • Windows Event Log Listener

In addition Network Performance Monitor also provides as a generic "Any" passive monitor for SNMP, Syslog, and Windows Event Log types. The Any passive monitor listens and receives all traps and events that occur on the device to which it is assigned. These pre-configured monitors display in the Monitor Library. As you configure new passive monitor types, they are added to the Monitor Library.

The Monitor Library displays passive monitors configured and available to apply to several network devices. For more information, see Passive monitors in the Monitor Library. In addition to configuring relevant monitors, you can assign passive monitors to the individual devices you want to monitor using device properties. For more information, see, Using Device Properties - Passive Monitors.