What it does
OpenNMS Horizon is an open-source network monitoring platform for local and distributed networks. It collects fault, performance, and traffic information and raises alarms, with documentation for SNMP polling and other integrations. Horizon is the project's rapid-release community distribution; the separate Meridian distribution uses a subscription for a more stable release cadence.
Start with a lab deployment
The Horizon installation guide describes a single-node setup that installs Horizon and PostgreSQL together, then signs in to the web UI and changes the default administrator password. That configuration is a starting point for learning, not a production recipe: the guide explicitly says it is not optimized for production or large networks. A real deployment needs planned database and time-series storage, capacity, network reachability, and secure credentials.
Once the server is running, define which device information to collect. Horizon's SNMP Interface Poller documentation explains how to monitor interface status separately from the services the Service Assurance Monitor already checks. For a small lab, an operator could begin with a reachable SNMP-enabled switch and a few interfaces, then add thresholds or alarms after confirming that the expected values arrive. This is an example of how to use the documented capabilities, not a test performed here.
Horizon is the community project's rapid-release distribution and is licensed under AGPLv3. OpenNMS Meridian is a related, curated subscription distribution; compare its support and release model separately rather than treating it as the same offer.
Strengths
- Combines fault, performance, and traffic monitoring with alarm generation for network environments.
- Official docs cover both installation and SNMP-specific monitoring behavior.
- The Horizon distribution is published as AGPLv3 open-source software.
Watch out for
- The standard installation includes a PostgreSQL dependency and requires the operator to manage the server and database.
- The documentation warns that the default single-node setup is not production-optimized, so larger deployments need additional capacity planning.
Best for
- Network teams that want an open-source platform for device health, performance, traffic, and alarms.
- Operators able to manage a self-hosted monitoring stack and its database.
- Engineers who need to extend SNMP-based monitoring for local or distributed networks.
Sources
- OpenNMS Horizon, Monitoring Community Distribution (Oct 25, 2026)
- OpenNMS Horizon Installation and Configuration (Oct 25, 2026)
- SNMP Interface Poller (Oct 25, 2026)
- OpenNMS Frequently Asked Questions (Oct 25, 2026)
- OpenNMS source repository (Oct 25, 2026)
- GNU Affero General Public License version 3 (Oct 25, 2026)