OpenNMS

Free plan APILinuxSelf-hostedWeb

What OpenNMS is

OpenNMS is an open-source platform for monitoring network faults, performance, traffic, and alarms across local and distributed networks. It is available as Horizon, a free community distribution that releases newer features early, and Meridian, a stable subscription version. Horizon features may not all be production-ready. Data collection supports protocols and services including SNMP, JSON, SQL, HTTP, VMware, and Prometheus, among others. Traffic monitoring supports NetFlow v.5/9, IPFIX, and sFlow, with stated capacity of 300,000+ flows per second. Minions can monitor remote devices and services beyond the Core’s reach, including behind firewalls or NAT when connected through ActiveMQ or Apache Kafka. Integrations include email, Slack, Mattermost, Jira, Remedy, Grafana, webhooks, and a REST API. The Grafana plugin can show alarms, outages, KPIs, NetFlow visualizations, and data aggregated from multiple instances. Meridian subscriptions include support options and severity-based SLAs; standard coverage is 7 a.m. to 7 p.m. ET on weekdays, with 24/7 emergency support as an add-on. Listed deployment options include self-hosted.

Who it suits

OpenNMS suits teams monitoring local or distributed networks that need fault, performance, traffic, and alarm visibility. Horizon is the free community option; Meridian is for those seeking a stable subscription and support options.

What it does well

Horizon community distribution is free
Monitors remote devices through Minions
Supports multiple traffic-flow formats
Grafana plugin displays alarms, outages, and KPIs

What to know first

Horizon features may not be production-ready
24/7 emergency support costs extra
Support plans exclude several third-party products
Meridian subscriptions are limited per instance

Limits

Horizon is free, but releases early and often, and some features may not be production-ready. Meridian subscriptions are limited per instance, and each software instance requires a subscription; the Basic plan costs $6,000 a year and includes 2 Meridian Cores.

Plans

Plan	Billed and limits	Price
Horizon	Free · Community distribution · Releases early and often · Features may not all be production-ready	Free
Standard	$12,000 / yr · 2 Meridian Cores · Up to 1000 Devices · Meridian Core Repository	$12,000 a year
Essential	$49,000 / yr · Up to 2 Meridian Cores and 10 Minions · Meridian Core and Minion Repository	$49,000 a year
Basic	$6,000 / yr · 2 Meridian Cores · Meridian Core Repository	$6,000 a year
Premier	$66,000 / yr · Up to 4 Meridian Cores and 25 Minions · Meridian Core, Minion, and Sentinel Repository	$66,000 a year
Premier+	Contact us · More than 4 Meridian Cores and more than 25 Minions · Core, Minion, and Sentinel Repository plus container images	On request

As opennms.com lists them, read 7 Oct 2026. The maker's own page has the final word.

Getting started

Choose Horizon, the free community distribution, or a Meridian subscription.
Deploy OpenNMS in a self-hosted environment.
Use the listed data collection protocols to connect monitoring sources.
For remote devices and services the Core cannot reach, use Minions connected through ActiveMQ or Apache Kafka.
Connect listed integrations such as Grafana, email, Slack or the REST API as needed.

Verdict

OpenNMS covers network monitoring across local and remote environments, with Horizon and Meridian serving different release and subscription needs. Consider Horizon’s production-readiness caveat and Meridian’s per-instance subscription limits when selecting a distribution.

Questions

Is OpenNMS free?

Horizon is free. Meridian is subscription-based, with the Basic plan listed at $6,000 a year.

What is the difference between Horizon and Meridian?

Horizon is the free community distribution with newer features. Meridian is the optimized stable subscription version.

Which platforms are listed for OpenNMS?

Its listed platforms are API, Linux, self-hosted and web.

What integrations does OpenNMS support?

Listed integrations include email, Slack, Mattermost, custom scripts or webhooks, Jira, Remedy, TSRM, Grafana and a REST API.

What support comes with Meridian?

Meridian subscriptions include support options and severity-based SLAs. Standard coverage is 7 a.m. to 7 p.m. ET Monday through Friday; 24/7 emergency support is an add-on.

Does OpenNMS set a device limit?

OpenNMS states there is no built-in per-instance device or alarm limit. Meridian subscriptions are limited per instance, and each software instance requires a subscription.

Facts from OpenNMS's own pages

Collection protocols: Its data collection supports SNMP, JSON, WinRM, XML, SQL, JMX, SFTP, FTP, JDBC, HTTP, HTTPS, VMware, WS-Management, and Prometheus. · opennms.com, 7 Oct 2026
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. · opennms.com, 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. · opennms.com, 7 Oct 2026
Founded: 2000 · opennms.com, 28 Sept 2026
Headquarters: Lewisville, Texas, United States · opennms.com, 28 Sept 2026
Integrations: The FAQ lists email, Slack, Mattermost, custom scripts or webhooks, Jira, Remedy, TSRM, Grafana, and a REST API among integrations. · opennms.com, 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. · opennms.com, 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. · opennms.com, 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. · opennms.com, 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. · opennms.com, 7 Oct 2026
Support limits: OpenNMS support plans do not cover Linux, PostgreSQL, Grafana, Cassandra, Kafka, or Elasticsearch as third-party products. · opennms.com, 7 Oct 2026
Traffic monitoring: It supports NetFlow v.5/9, IPFIX, and sFlow, with stated capacity of 300,000+ flows per second. · opennms.com, 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. · opennms.com, 7 Oct 2026
Visualization: The OpenNMS Grafana plugin can display alarms, outages, KPIs, NetFlow visualizations, and data aggregated from multiple OpenNMS instances. · opennms.com, 7 Oct 2026
Zero-trust: OpenNMS describes zero-trust configurations that use encryption within private networks and strong authentication between authorized parties. · opennms.com, 7 Oct 2026

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