Nagios Core - Passive Monitoring

Preface

In this document I'd like to explain meaning of Passive Monitoring.

Passive Monitoring - Explanation

The easiest way how to understand manning of Passive Monitoring is to read next description:

Who is doing the polling?

- In this case we can not speak about standard polling. In most of the cases the monitored object itself is reporting to monitoring server all interesting issues.

Who is doing validation of polled data?

- In this case validation of measured data (and comparing them to thresholds) is done out of monitoring system. In most of the cases it’s done at monitored object itself. In this concept only interesting event will be sent to monitoring system to be handled as an alarm.

Who is deciding if alarm will be created?

- In most of the cases when passive monitoring is used monitored object itself is deciding which event will be repotted to monitoring system to be handled as an alarm.

Passive Monitoring - Advantage

Polling Management

- In most of cases it’s possible to say that the “polling” is scheduled and managed from monitored object itself.

Polling Interval

- In general at this monitoring concept we can say that the issue with setting correct polling interval is not present.

- The reason for this, is that monitored object is sending notification for each of interesting event in real time to monitoring server. According to this it’s not really common to overlook some interesting event using this monitoring concept.

Utilization of resources

Passive Monitoring:
- Is preventing usage of periodical polling of interesting parameters at site of monitoring sytem.
- Is reducing usage of additional software/script that are periodically running on monitoring server or monitored object.

According to mentioned points, it’s important to understand that we are saving our resources.

Passive Monitoring - Disadvantage

Flexibility

- In this case we need to accept communication protocols of 3th part providers. In most of the cases it mean to create additional scripts that will provide the integration between 3th part application and out monitoring system.

Lack of support

In some cases provider of monitored object isn’t providing sufficient support for passive monitoring.

Like:
- Lack of SNMP trap notifications
- Lack of Syslog notifications
- Lack of Application Log Files
- Lack of Event Logging
- Lack of event logging in to Event Viewer
- Lack of possibility to call script with parameters in case that interesting issue is present.

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