Cacti vs OpenNMS: What are the differences?

# Introduction
This markdown provides key differences between Cacti and OpenNMS.

1. **Data Collection and Monitoring**:
Cacti mainly focuses on monitoring network bandwidth usage through SNMP polling, while OpenNMS offers comprehensive monitoring capabilities beyond just network bandwidth, including applications, servers, and services.

2. **Alerting and Notification**:
Cacti lacks advanced alerting and notification features, requiring additional plugins or scripts to enable alerts. In contrast, OpenNMS provides robust alerting and notification mechanisms out of the box, supporting various notification methods like email, SMS, and integrations with other tools.

3. **Scalability**:
Cacti is suitable for small to medium-scale environments due to its limitations in scaling horizontally. OpenNMS, on the other hand, is designed for large-scale deployments, offering scalability and flexibility to manage extensive networks and multiple sites.

4. **Discovery and Auto-provisioning**:
OpenNMS includes automated network discovery and auto-provisioning features, simplifying the process of adding new devices to the monitoring system. Cacti requires manual setup for each device, making it less efficient for large and dynamic network environments.

5. **Customization and Extensibility**:
Cacti provides a user-friendly interface for creating custom graphs and templates but lacks flexibility in extending monitoring capabilities beyond predefined metrics. OpenNMS offers extensive customization options through its flexible architecture, allowing users to integrate custom plugins and extensions easily.

6. **Community and Support**:
While both Cacti and OpenNMS have active user communities, OpenNMS has a more extensive network of users and contributors, leading to faster bug fixes, updates, and community-driven enhancements compared to Cacti.

In Summary, this markdown highlights key differences between Cacti and OpenNMS, including their focus on data collection, alerting capabilities, scalability, automation features, customization options, and community support.