Vol. 1 · Reviewed September 29, 2026

Monitoring software, reviewed for the person who ends up on call.

Independent reviews of self-hosted and open-source monitoring — and the commercial tools worth paying for — built from vendor documentation and what admins report about disk growth, poller load and pages per week.

Read the reviews How we review

Abstract illustration of monitoring graphs and status lights

The check log

One line per product: the thing that is fine, the thing to watch, and the thing that might rule it out.

ZabbixOpen source
WARN History and trend tables grow fast — plan partitioning or TimescaleDB early
Nagios CoreOpen source
WARN Every host and service lives in hand-edited object files
IcingaOpen source
WARN Several moving parts: Icinga 2, Icinga DB, Redis, Icinga Web
CheckmkOpen core
WARN Some features you will want (agent bakery, faster core) are in paid editions
LibreNMSOpen source
WARN Default five-minute polling hides short spikes; faster polling costs CPU
PRTG Network MonitorCommercial
WARN Licensing is by sensor count, and sensors add up faster than you expect
ManageEngine OpManagerCommercial
WARN Flow analysis and config backup are separate add-ons with their own pricing
SolarWinds NPMCommercial
WARN Needs Windows Server plus SQL Server capacity of its own
Angry IP ScannerOpen source
WARN A point-in-time snapshot: nothing is stored, scheduled or alerted on
WiresharkOpen source
WARN Captures need privileges, disk space and a careful filter to stay useful
LizardSystems Network ScannerFree / paid
WARN Latest release is v21.07 from July 2021; Windows 11 is not on the vendor’s supported list

WARN = the operational cost to plan for. Each review adds the OK and CRIT lines. Editorial verdicts, not live data.

Independent — 7 of 11 products we cover are open source or open core We host no files; links go to vendors’ own sites No affiliate links — product links go straight to official sites

Comparisons

Open-Source Monitoring

The license is free. The hours are not. This table compares the open-source monitors we see most in small and mid-size shops, plus one commercial yardstick.

Zabbix · Nagios Core · Icinga · Checkmk · LibreNMS · PRTG Network Monitor

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SNMP & Network Device Monitoring

Interfaces, errors, CPU on the core switch, the firewall that fills its session table every Friday. Here is how the main tools handle the gear that is not a server.

LibreNMS · Zabbix · Checkmk · PRTG Network Monitor · ManageEngine OpManager · SolarWinds NPM · Nagios Core

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Server & Service Monitoring

Disk full, service stopped, certificate expiring in nine days. This table compares tools on how well they catch the ordinary failures that make up most on-call nights.

Zabbix · Checkmk · Icinga · Nagios Core · PRTG Network Monitor · ManageEngine OpManager

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Network Discovery & Troubleshooting

A monitor only watches what you told it about, and it only reports what reached the poller. This table covers the tools that fill both gaps.

Wireshark · Angry IP Scanner · LibreNMS · Zabbix · Checkmk · PRTG Network Monitor · LizardSystems Network Scanner

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What we look at

Six questions every review answers

Time to first dashboard: Hours from an empty VM to a screen someone would actually leave open on the wall.
Database growth: What history and trends cost on disk after 90 days at one-minute polling, and how the tool prunes them.
Poller sizing: When one box stops being enough, and whether proxies or satellites keep collecting through a WAN outage.
Template quality: Whether the stock checks for Linux, Windows and common switches are sensible or need rewriting.
Alert noise: Dependencies, flapping detection and maintenance windows — the features that decide if people keep reading pages.
Upgrade pain: What the last two major upgrades involved: schema migrations, config rewrites, downtime.

The full methodology explains our sources, the scoring and what we will not do.

On the desk

Guides and head-to-heads

Head to head

Icinga vs Nagios Core: stay, fork or rebuild?Icinga 2 vs Nagios Core compared on configuration, APIs, distributed monitoring, web UI and plugin compatibility, with guidance on when staying on Nagios is fine.
LibreNMS vs PRTG: open-source NMS or a paid subscription?LibreNMS vs PRTG Network Monitor for switch, router and firewall monitoring: discovery, licensing by sensor, hosting options, alerting and the real cost of running each.
Zabbix vs Checkmk: which self-hosted monitor fits your team?Zabbix vs Checkmk from an operator's view: data model, discovery, storage growth, licensing, upgrades and alerting, with a clear pick-this-if verdict.

Guides

Cutting alert noise: thresholds, dependencies and flappingHow to stop a monitoring system from paging for nothing: trigger hysteresis, dependencies, maintenance windows and flap detection in Zabbix, Icinga and Checkmk.
How big should your monitoring server be?Sizing a Zabbix (or similar) monitoring server from first principles: items, NVPS, history vs trends, housekeeping, partitioning and proxies, with a worked example.
Moving off Nagios Core: a migration plan that doesn't lose checksInventory, parallel run, plugin reuse and cutover: a step-by-step plan for replacing Nagios Core with Icinga 2 or another monitor without silent gaps.
Setting up SNMPv3 on switches and routers for monitoringA practical SNMPv3 authPriv setup for Cisco IOS and Linux net-snmp, with snmpwalk tests, the errors you will actually see, and how to add devices to LibreNMS.

The standing rules

Scannethub is not a vendor, a reseller or a mirror. We do not host installation packages or archives, and every product link points at the maker’s own website. When you need the software itself, ourwhere-to-get page explains how to use signed package repositories and verify checksums.

Our reviews include what goes wrong. Every product page carries a section on where it falls short and who should skip it, because a monitoring system you outgrow in a year costs more than the license ever did. Questions or corrections go to editor@scannethub.biz.