Active Checks in Nagios: Best Practices and Configuration

Nagios, a widely used open-source monitoring system, empowers system administrators to keep a vigilant eye on their network infrastructure’s health. One of its core features, active checks, plays a pivotal role in proactively monitoring various aspects of your systems. In this article, we will delve into the best practices for configuring and utilizing active checks effectively within Nagios.

Understanding Active Checks

Active checks involve Nagios taking the initiative to actively query monitored devices and services at scheduled intervals. This proactive approach provides real-time insights into the health and performance of your infrastructure. Unlike passive checks, where monitored devices push data to Nagios, active checks ensure constant monitoring even when the monitored devices can’t independently send information.

Benefits of Active Checks

Active checks offer several advantages. They enable continuous monitoring regardless of network conditions or device status, guaranteeing prompt detection of issues. This approach is particularly useful for remote devices or those behind firewalls that restrict external access. Additionally, active checks ensure consistent data collection, helping to establish a reliable baseline for performance analysis and trend identification.

Configuration Steps

1. Defining Check Commands

Begin by defining check commands in Nagios configuration. These commands specify what checks to perform and how to execute them. You can use plugins to perform checks for services like HTTP, DNS, or disk usage. Configure command arguments, thresholds, and timeouts according to your monitoring requirements.

2. Setting Up Hosts and Services

Next, configure the hosts and services you want to monitor. Associate the defined check commands with specific hosts and services. Specify the frequency of active checks to strike a balance between timely updates and reduced network load.

3. Fine-tuning Notifications

Configure notification settings to receive alerts when issues arise. Define contact groups, notification intervals, and escalation procedures. This ensures that the right personnel are promptly informed of any anomalies.

Best Practices

Avoid Overloading Targets

Set appropriate check intervals to avoid overloading the monitored devices. Frequent checks can strain resources and impact the system’s performance.

Regularly Review Thresholds

Regularly review and update threshold values for different checks. As your infrastructure scales, optimal thresholds may change, and timely adjustments prevent false positives or missed alerts.

Implement Check Dependencies

Define check dependencies to prevent unnecessary notifications. For instance, if a router goes down, it’s more relevant to receive alerts about the dependent switches than inundating with redundant notifications.

Use Parallelization

Leverage Nagios’ capability to parallelize active checks across multiple instances. This enhances efficiency and reduces the time required for comprehensive monitoring.


Mastering active checks in Nagios empowers administrators to maintain a proactive stance in network monitoring. By understanding the core concepts, benefits, and best practices, you can configure a robust monitoring framework that ensures the health, performance, and reliability of your IT infrastructure. Stay vigilant, identify issues swiftly, and keep your systems running smoothly with Nagios’ active checks.

Related Articles