OpenNMS has had its ups and downs between versions, but has always been reliable and free monitoring. There are a lot of features that can be enabled with OpenNMS through the browser, but some will require having to open a text editor and manually creating or editing a text file. While there is a learning curve to this monitoring system if you've had experience with other monitoring systems, there is a very large support group that is always helpful.

Easy to use after configuration. Feature-rich. Supports escalations and different contact groups.

Not the easiest to configure for multiple groups supported.

OpenNMS is highly customizable and extensible, allowing users to tailor it to their specific needs and integrate it with other tools and platforms. OpenNMS provides advanced monitoring and reporting capabilities, including real-time performance monitoring, threshold-based alerts, and customizable reports. OpenNMS is designed to be highly scalable and reliable, making it a good choice for large-scale network management. OpenNMS has an active and supportive community that contributes to its development and provides support and resources for users.

OpenNMS can have a steep learning curve, especially for users who are not familiar with network management concepts and terminology. Setting up and configuring OpenNMS can be complex and time-consuming, requiring some technical expertise. While OpenNMS supports a wide range of technologies and platforms, it may not support all technologies and platforms used in your environment. OpenNMS's documentation can be limited and difficult to navigate, making it difficult for some users to get started.