OpenNMS
OpenNMS is an open-source platform for monitoring faults, performance and traffic and generating alarms across local and distributed networks.
What OpenNMS is
OpenNMS is an open-source platform for monitoring faults, performance and traffic and generating alarms across local and distributed networks. It comes in two distributions: Horizon, a free community edition with newer features, and Meridian, a stable subscription version. Horizon releases frequently, and some features may not be production-ready. Data collection supports protocols and services including SNMP, JSON, WinRM, XML, SQL, JMX, SFTP, FTP, JDBC, HTTP, HTTPS, VMware, WS-Management and Prometheus. Traffic monitoring supports NetFlow v.5/9, IPFIX and sFlow, with stated capacity above 300,000 flows per second. Minions can monitor remote devices and services the Core cannot reach, including behind firewalls or NAT when connected through ActiveMQ or Apache Kafka. Integrations include email, Slack, Mattermost, scripts or webhooks, Jira, Remedy, TSRM, Grafana and a REST API. A Grafana plugin can display alarms, outages, KPIs, traffic visualizations and data aggregated from multiple instances. Meridian subscriptions include support options and severity-based SLAs; listed standard coverage is weekdays, with emergency 24/7 support as an add-on.
Good
- Horizon offers a free community distribution.
- Supports numerous collection protocols and services.
- Minions can reach remote sites behind firewalls or NAT.
- Integrates with Grafana, collaboration tools and a REST API.
- No built-in per-instance device or alarm limit.
Watch out
- Horizon features may not be production-ready.
- Meridian subscriptions are limited per instance.
- Each software instance requires a Meridian subscription.
- 24/7 emergency support is an add-on.
Who it suits
OpenNMS suits teams monitoring local and distributed networks that want a free community edition or a Meridian subscription. Its Minions and integrations may suit organizations with remote locations or existing monitoring workflows.
Verdict
OpenNMS offers broad monitoring coverage and a free community distribution alongside subscription support options. Teams evaluating Meridian should account for per-instance subscription limits and the scope of included support.
Plans and prices
From OpenNMS's own pricing page, checked 7 Oct 2026.
| Plan | Price | What it gives you |
|---|---|---|
| Horizon | Free | Community distribution · Releases early and often · Features may not all be production-ready · Free |
| Basic | $6,000 a year | 2 Meridian Cores · Meridian Core Repository · $6,000 / yr |
| Standard | $12,000 a year | 2 Meridian Cores · Up to 1000 Devices · Meridian Core Repository · $12,000 / yr |
| Essential | $49,000 a year | Up to 2 Meridian Cores and 10 Minions · Meridian Core and Minion Repository · $49,000 / yr |
| Premier | $66,000 a year | Up to 4 Meridian Cores and 25 Minions · Meridian Core, Minion, and Sentinel Repository · $66,000 / yr |
| Premier+ | Priced on request | More than 4 Meridian Cores and more than 25 Minions · Core, Minion, and Sentinel Repository plus container images · Contact us |
The facts
Each one read from OpenNMS's own pages, with the date it was checked.
What it does
- Collection protocols
- Its data collection supports SNMP, JSON, WinRM, XML, SQL, JMX, SFTP, FTP, JDBC, HTTP, HTTPS, VMware, WS-Management, and Prometheus.checked 7 Oct 2026
- Distributed monitoring
- Minions monitor devices and services at remote locations that the OpenNMS Core cannot reach, including behind firewalls or NAT when connected through ActiveMQ or Apache Kafka.checked 7 Oct 2026
- Integrations
- The FAQ lists email, Slack, Mattermost, custom scripts or webhooks, Jira, Remedy, TSRM, Grafana, and a REST API among integrations.checked 7 Oct 2026
- Purpose
- OpenNMS is an open-source network monitoring platform for fault, performance, traffic monitoring, and alarm generation across local and distributed networks.checked 7 Oct 2026
- Scaling and license limits
- OpenNMS states there is no built-in per-instance device or alarm limit, while Meridian subscriptions are limited per instance and each software instance requires a subscription.checked 7 Oct 2026
- Security
- The company says its security program aligns with ISO 27001/27002, CCPA, and GDPR frameworks, and major Meridian versions receive third-party penetration testing and remediation before release.checked 7 Oct 2026
- Support
- Meridian subscriptions include support options and severity-based SLAs; the listed standard coverage is 7 a.m. to 7 p.m. ET Monday through Friday, with 24/7 emergency support as an add-on.checked 7 Oct 2026
- Support limits
- OpenNMS support plans do not cover Linux, PostgreSQL, Grafana, Cassandra, Kafka, or Elasticsearch as third-party products.checked 7 Oct 2026
- Traffic monitoring
- It supports NetFlow v.5/9, IPFIX, and sFlow, with stated capacity of 300,000+ flows per second.checked 7 Oct 2026
- Two distributions
- OpenNMS is available as Meridian, an optimized stable subscription version, and Horizon, a free community distribution with the newest features.checked 7 Oct 2026
- Visualization
- The OpenNMS Grafana plugin can display alarms, outages, KPIs, NetFlow visualizations, and data aggregated from multiple OpenNMS instances.checked 7 Oct 2026
- Zero-trust
- OpenNMS describes zero-trust configurations that use encryption within private networks and strong authentication between authorized parties.checked 7 Oct 2026
The company
- Company
- The OpenNMS Group says it was founded in 2004 and provides services from headquarters near Research Triangle, North Carolina; its site contact address is in Lewisville, Texas.checked 7 Oct 2026
- Founded
- 2000checked 28 Sep 2026
- Headquarters
- Lewisville, Texas, United Stateschecked 28 Sep 2026
Alternatives to OpenNMS
- 1
Wazuh
Free planOpen sourceWebAPILinuxmacOS8.4From $571 a month - 2
PagerDuty
Free planAndroidiOSWebAPI8.3From $21 a month - 3
xMatters
Free planAndroidiOSWebAPI8.3From $15 a month - 4
AlertOps
Free planAndroidiOSWebAPI8.1From $8 a month - 5
MISP
Free planOpen sourceWebAPILinuxSelf-hosted7.9From €7.31 a year - 6
UTMStack
Open sourceWebAPILinuxmacOS7.9From $238.80 a month