What is the best free network monitoring tool?

Zabbix is the most capable free option overall — SNMP, agents, auto-discovery and flexible alerting at no licence cost. LibreNMS is easier to start with for SNMP-heavy network estates, and Prometheus with Grafana is the better choice if your focus is services and time-series metrics rather than classic network hardware.

What is the difference between network monitoring and server monitoring?

Network monitoring watches the devices and links that carry traffic — switches, routers, firewalls, interfaces, bandwidth and latency. Server monitoring watches the machines themselves — CPU, memory, disk, services and logs. Most teams need both, ideally in one place so an alert can be traced end to end.

Do I need NetFlow or is SNMP enough?

SNMP tells you a link is saturated. NetFlow or sFlow tells you which host, application or conversation is saturating it. If you regularly need to answer 'who is using the bandwidth', add flow collection; otherwise interface counters via SNMP are usually enough.

Do I need separate tools for network and server monitoring?

Not necessarily. Several tools cover both, and keeping them together means one alerting path and one on-call rota. [Server monitoring tools](/blog/server-monitoring-tools) compares the server-focused options, and Infronest includes [network](/services/network-monitoring) and [server monitoring](/services/server-monitoring) in the same workspace.

What is SNMP monitoring and why use SNMP v3?

SNMP is the protocol network devices use to report health — interface counters, CPU, memory, temperature — to a monitoring system that polls them. Insist on SNMP v3 because it adds authentication and encryption; the still-common v2c sends community strings (effectively credentials) in clear text on your network.

How much does network monitoring software cost?

Open-source tools such as Zabbix, LibreNMS and Nagios Core are free but cost engineering time to deploy and maintain. Commercial products price by device and interface count, sensors (PRTG) or usage (Datadog), so count your devices and interfaces before comparing quotes. Published prices vary by vendor — model the bill at your projected scale, not today's.

Which network monitoring tool is best for MSPs?

Prioritise multi-tenancy and per-client isolation over raw feature count — bolting them on later is painful. Auvik is a popular cloud-based choice built around multi-client network visibility, and RMM platforms bundle monitoring with patching and remote access if you need more than network telemetry per client.

Network Monitoring Tools Compared

Network monitoring tools watch the availability, performance and health of your switches, routers, firewalls and links, and alert you when something degrades.

The practical choice is between free tools that cost engineering time to run (Zabbix, LibreNMS, Nagios) and commercial tools that cost licence fees instead (PRTG, SolarWinds, Datadog).

3: things to monitor: availability, performance, device health
SNMP v3: the version to insist on — v2c sends credentials in clear text
2: cost models: free tool + your time, or licence + faster setup

Network problems are rarely announced. A switch port flaps, a link saturates, a device drops off — and the first you hear is a user saying 'the internet is slow'. Network monitoring tools exist to tell you first, with evidence.

The problem

Why most network monitoring gets switched off

Almost every team that has abandoned a monitoring tool abandoned it for the same reason: it cried wolf. Someone deployed it, enabled every check on every device, accepted the default thresholds, and within two weeks the on-call channel was so noisy that nobody read it. The tool kept running and stopped mattering.

Monitoring only earns trust when an alert reliably means something is wrong. That is a configuration discipline rather than a product feature, and it is why the section on common mistakes below matters more than the comparison table above it.

Alert fatigue — everything monitored at once, so nothing gets read
Default thresholds — 90% CPU on a firewall is not 90% on a test server
No maintenance windows — planned reboots page the on-call engineer
Blind spots — the one uplink nobody added is the one that fails
No escalation path — alerts land in an inbox with no owner

Basics

What network monitoring tools do

Network monitoring software continuously checks the availability, performance and configuration of the devices that carry your traffic — routers, switches, firewalls, access points, servers and links between sites.

Availability — is the device up, is the link alive, how long has it been down
Performance — bandwidth utilisation, latency, packet loss, interface errors
Device health — CPU, memory and temperature on network hardware via SNMP
Topology — what is connected to what, and which IP sits on which port
Alerting — notify the right person when a threshold breaks, before users notice
Logging — syslog collection so you can reconstruct what happened and when

Open source

Best open-source network monitoring tools

Open-source monitoring is genuinely capable — several of these run in large enterprises — but the licence saving is paid back in setup and maintenance time. Choose one of these if you have someone who will own it.

Zabbix — the most capable free option: SNMP, agents, auto-discovery, templates, flexible alerting. Steep initial setup but genuinely enterprise-grade.
Nagios Core — the long-standing classic. Extremely extensible through plugins, but the UI and configuration feel dated and everything is a config file.
LibreNMS — auto-discovery-first, very good SNMP support and a far friendlier UI than Nagios. Excellent for network-device-heavy estates.
Prometheus + Grafana — the modern metrics stack. Superb for time-series and dashboards; better suited to infrastructure and services than to classic SNMP network gear.
Icinga 2 — a Nagios fork with a modern API, better config language and a usable web UI.

Commercial

Best commercial network monitoring tools

Commercial tools mostly sell time: faster deployment, supported upgrades and someone to call. The pricing models differ sharply, so count your devices and interfaces before comparing quotes.

SolarWinds NPM — deep network-specific feature set (NetPath, topology, config management). Powerful, priced for larger estates.
PRTG (Paessler) — sensor-based licensing, quick to deploy, popular with small and mid-size teams. Cost rises with sensor count.
Datadog Network Monitoring — strong if you are already using Datadog for infrastructure and APM; usage-based pricing can climb fast.
ManageEngine OpManager — broad feature coverage at mid-market pricing, common in India.
Auvik — cloud-based, network-focused, popular with MSPs for multi-client visibility.

Infronest includes network monitoring alongside server monitoring, assets and helpdesk — so an alert becomes a ticket against a known device rather than an email.

Explore Infronest network monitoring

At a glance

Network monitoring tools compared

The table condenses the open-source and commercial picks above into one view. Licence and pricing structures change, so verify the row you shortlist against the vendor's current terms.

Open-source and commercial network monitoring tools at a glance

Tool	Licence	Best for	Watch out for
Zabbix	Free, open source	Enterprise-grade monitoring at no licence cost	Steep initial setup
Nagios Core	Free, open source	Plugin-based extensibility	Dated UI; everything is a config file
LibreNMS	Free, open source	SNMP-heavy, network-device estates	Network-device focus — pair with server monitoring
Icinga 2	Free, open source	Nagios power with a modern API and config language	—
SolarWinds NPM	Commercial	Deep network features: NetPath, topology, config management	Priced for larger estates
PRTG (Paessler)	Commercial	Quick deployment for small and mid-size teams	Cost rises with sensor count
Datadog Network Monitoring	Commercial	Teams already on Datadog for infrastructure and APM	Usage-based pricing can climb fast
ManageEngine OpManager	Commercial	Broad coverage at mid-market pricing	—
Auvik	Commercial	MSPs needing multi-client network visibility	—

How to choose a network monitoring tool

Six checks separate a tool that survives its first quarter from one that gets switched off. Work through them before you shortlist, not after. If servers matter as much as network gear, read server monitoring tools alongside this.

Count your devices and interfaces first — most commercial pricing keys off exactly this, and it decides your budget more than features do.
Check SNMP v3 support and how easy it is to add a device type you own that is not in the default templates.
Check alert routing — email is not enough; you want Slack/Teams, on-call escalation and a way to suppress noise during maintenance.
Decide if you need flow data (NetFlow/sFlow) for bandwidth attribution, or whether interface counters are enough.
If you are an MSP, multi-tenancy and per-client isolation are non-negotiable — bolting that on later is painful. If you also need patching and remote access per client, compare RMM tools instead of a monitoring-only product.
Consider whether you want network monitoring as a separate tool at all, or inside the platform that already holds your servers, assets and tickets.

Common mistakes teams make

These four mistakes account for most abandoned monitoring deployments. All of them are configuration decisions rather than product limitations, which means they are avoidable whichever tool you pick.

Monitoring everything at once — alert fatigue sets in and real alerts get ignored. Start with links, core switches and internet edge.
No maintenance windows — every planned reboot pages the on-call engineer, so alerts stop being trusted.
Thresholds copied from defaults — 90% CPU on a firewall means something different from 90% on a test server.
Monitoring devices but not the paths users actually take — a healthy switch does not prove the application is reachable.

Infronest

Conclusion

Infronest includes network monitoring — SNMP polling, device and IP mapping, latency and interface visibility, syslog ingest and incident workflows — in the same tenant-isolated workspace as server monitoring, IT assets, helpdesk and patching. An alert becomes a ticket against a known asset instead of an email nobody owns.

Start a 14-day free trial at infronest.com — no credit card required.

One workspace for network, server and website monitoring with alerts that open real tickets. 14-day free trial, no credit card required.

Book a monitoring demo

Explore network monitoring →

Frequently Asked Questions

What is the best free network monitoring tool?: Zabbix is the most capable free option overall — SNMP, agents, auto-discovery and flexible alerting at no licence cost. LibreNMS is easier to start with for SNMP-heavy network estates, and Prometheus with Grafana is the better choice if your focus is services and time-series metrics rather than classic network hardware.
What is the difference between network monitoring and server monitoring?: Network monitoring watches the devices and links that carry traffic — switches, routers, firewalls, interfaces, bandwidth and latency. Server monitoring watches the machines themselves — CPU, memory, disk, services and logs. Most teams need both, ideally in one place so an alert can be traced end to end.
Do I need NetFlow or is SNMP enough?: SNMP tells you a link is saturated. NetFlow or sFlow tells you which host, application or conversation is saturating it. If you regularly need to answer 'who is using the bandwidth', add flow collection; otherwise interface counters via SNMP are usually enough.
Do I need separate tools for network and server monitoring?: Not necessarily. Several tools cover both, and keeping them together means one alerting path and one on-call rota. Server monitoring tools compares the server-focused options, and Infronest includes network and server monitoring in the same workspace.
What is SNMP monitoring and why use SNMP v3?: SNMP is the protocol network devices use to report health — interface counters, CPU, memory, temperature — to a monitoring system that polls them. Insist on SNMP v3 because it adds authentication and encryption; the still-common v2c sends community strings (effectively credentials) in clear text on your network.
How much does network monitoring software cost?: Open-source tools such as Zabbix, LibreNMS and Nagios Core are free but cost engineering time to deploy and maintain. Commercial products price by device and interface count, sensors (PRTG) or usage (Datadog), so count your devices and interfaces before comparing quotes. Published prices vary by vendor — model the bill at your projected scale, not today's.
Which network monitoring tool is best for MSPs?: Prioritise multi-tenancy and per-client isolation over raw feature count — bolting them on later is painful. Auvik is a popular cloud-based choice built around multi-client network visibility, and RMM platforms bundle monitoring with patching and remote access if you need more than network telemetry per client.

About the Author

Infronest

Infronest Product & IT Operations Team

We build and operate monitoring, patching and endpoint agents across Windows, macOS, Linux and Android in production for real customers. Guidance here reflects what these tools genuinely do in live environments.

Written by the Infronest Product & IT Operations Team. We run SNMP polling, flow analysis and syslog ingest in production; tool notes reflect real deployment experience.