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Open-Source and Closed-Source Monitoring Tools Compared

Today, we’re comparing open-source and closed source monitoring tools. Our goal is not to start a never-ending debate but to give you an idea of what’s available. Although proponents of one are typically enemies of the other, our take on the subject is that there is good and bad software in each category. We’ll be reviewing some of the best products of either type. As you’ll see, there are plenty of good options in either category.

Open-Source and Closed-Source Monitoring Tools

We’ll start by explaining what open-source software is and follow by comparing several aspects of each distribution model. We’ll see how they compare on price but also on support, performance & reliability and customization. Then, we’ll address some security concerns related to open-source software before we complete our tour by reviewing some of the best free and open-source monitoring tools and some paid alternatives that you may prefer.

About Open-Source Software

When talking about open-source software, we are usually referring to a broader concept called free and open-source software. The free here is referring to freedom rather than the absence of cost. With free and open-source software, anyone is freely licensed to use, copy, study, and change the software in any way, and the source code is openly shared so that people are encouraged to voluntarily improve the design of the software. This is different from proprietary or closed-source software, where the software is generally under restrictive copyright licensing and the source code is typically hidden from users.

Some benefits of using free and open-source software include decreased software costs, increased security and stability, protecting privacy, education, and giving users more control over their own hardware. Today, free and open-source software is everywhere. For instance, operating systems such as Linux and descendants of BSD are in widespread use and are powering millions of servers. Free-software licenses and open-source licenses are also used by many software packages. Furthermore, the free-software movement and the open-source software movement are online social movements that are accessory to the widespread adoption of free and open-source software.

Comparing Open-Source and Closed-Source

There are several factors to consider when deciding whether to go with an open- or closed-source monitoring solution. While the cost—or lack thereof—factor may be a major draw, one should always consider all the angles. Let’s compare the advantages and disadvantages of both approaches on various factors such as price but also support, performance and reliability as well as customization. It will help you decide if you want to go one route or the other.


Most open-source monitoring tools are available free of charge. They can, therefore, provide an obvious cost-saving benefit to organizations because they don’t appear to require any financial investment. This is not always the case, though, and it is not uncommon to see an open-source monitoring solution require users to pay for extra features or added functionalities.

Although not directly related to the cost of monitoring tools, other factors to consider are legal issues and compliance regulations. Some regulatory frameworks specifically prohibit the use of open-source software. Also, some open-source software can only be used for non-commercial applications. Keep that in mind as infringements could end up costing you more than you expected.

As for closed-source monitoring tools, many vendors—if not all—offer a free trial period that allows you to test the products and ensure they meet your needs. Once the trial period is over, most paid monitoring tools will offer different levels or tiers of payments, typically based on the number of interfaces, nodes, or devices to be monitored.

The market has changed a lot in recent years. A while ago, one would typically purchase a monitoring tool from a reseller. Today, many vendors have moved to a direct e-commerce model and sell directly to customers through their websites. One advantage of this business model is that you can often benefit from various promotions the vendors may be offering. You should do a quick internet search for any applicable promotion codes you can use, especially towards the end of each quarter when vendors are looking to meet their sales goals.


Support is often the area where open-source software has the worst reputation. Without a big organization backing it up, it is true that “official” support is often tragically lacking in open-source software. However, community support is where the model shines. Online community-supported support forums are often available and, although you certainly won’t get any Service Level Agreement (SLA), the support you get from these sources is often adequate.

Be aware that the support you get with open-source software—not just monitoring tools for that matter—varies greatly. If you absolutely need rock-solid support, make sure you do your homework and verify that you’ll get the support that you need.

Paid solutions, on the other hand, typically come bundled with support that is backed by an organized structure with agents, SLAs and often round the clock availability. You can reasonably expect that any issue you might encounter will be quickly addressed and resolved to your satisfaction. However, the support offered varies quite a bit from vendor to vendor and this is an area that you should examine closely if support is one of your priorities.

Furthermore, makers of closed-source monitoring tools tend to offer better documentation that their open-source counterparts, somewhat alleviating the need for support in the first place. And just like in the open-source arena, several closed-source software platforms will also have community-driven forums where users can share tips and help each other.

Performance and Reliability

Performance and reliability is probably the area where there are the least differences between open- and closed-source software. Some will argue that the performance of open-source tools is largely dependent on community input and, as such, cannot possibly be as good as closed-source which is typically driven by commercial interests. Others will say that open-source software needs more frequent updating and patching.

My experience shows that none of this has any credence. I’ve seen rock-solid open-source software and absolutely crappy commercial one. Being backed by a large commercial organization in no way warrants quality, performance, or reliability. There is good software and bad software just as there is open-source and closed-source software but there is absolutely no correlation between the two.

Of course, closed-source commercial software tends to be easier to use and more polished than the open-source one. After all, their makers need to have something to convince customers to shell out important sums of money. But even that is not necessarily true.


Open-source software gives end-users access to the source code. That, in turn, allows them to modify the software to their specific needs. At first glance, that may appear to be the ultimate level of customization. But it’s actually a double-edged sword. Customizing open-source software will often entail writing code which is often beyond the reach of most users.

On the contrary, closed-source software often offers various levels of customization that can be applied without having to write any code. You won’t be able to add some extra functionality to such tools but if the level of customization you need deals with adapting the dashboard to your needs or preparing a report with some specific data, many of the commercial monitoring tools will let you do that.

How About Security?

Whether open-source—or closed-source, for that matter—software is more secure is an ongoing and probably never-ending debate. Detractors of open-source software will often argue that by virtue of making source code available, such software is more exposed to attacks, However, experience shows that open-source software generally has less malware written for it. Furthermore, supporters of open-source software argue that there are fewer exploits due to more frequent patches and the number of developers that are constantly contributing to the project’s security.

Many professionals will agree that closed-source software is more secure. This is partly due to its development model in a controlled environment by a trusted vendor. And whenever a vulnerability is discovered, reliable vendors will quickly work at developing and providing patches and updates to keep their customers out of trouble. Open-source resources often can’t compete with the security effort put into closed-source solutions.

The Best Open-Source Monitoring Tools (And Some Closed-Source Alternatives)

We’ve scoured the market looking for some of the best open-source monitoring tools. Our idea was to give you a good sample of what is available. But to make things more interesting, we’ll also be reviewing some commercial alternatives. Don’t expect a feature-for-feature match in any of the commercial alternatives we pin against open-source suggestions. Monitoring tools are all different and no two packages can support such a comparison. Instead, our comparisons are in terms of the general quality of each tool.

1. Zabbix

First on our list is Zabbix, a free and open-source product but that has a highly professional look and feel, much like what you’d expect from a commercial product. But the good looks of its user interface are not its only assets. The product also has an impressive feature set. It will monitor most network-attached devices in addition to networking equipment. It would be an excellent choice for anyone in need of monitoring servers in addition to network bandwidth utilization.

Zabbix Dashboard Screenshot

Zabbix uses SNMP as well as the Intelligent Platform Monitoring Interface (IMPI) for monitoring devices. You can use the software to monitor bandwidth, device CPU and memory utilization, general device health and performance as well as configuration changes, a rather unique feature within this list. This tool does way more than simple network bandwidth utilization monitoring. It also features an impressive and completely customizable alerting system that will not only send email or SMS alerts but also run local scripts which could be used to fix some issues automatically.

Alternative: SolarWinds Network Performance Monitor (FREE TRIAL)

SolarWinds, the maker of the Network Performance Monitor has been around for about 20 years and it enjoys a solid reputation for having made some of the best network and system administration tools. Many of the company’s products have received rave reviews and are considered among the very best in their respective fields. The company is also famous for its free tools, each addressing a specific need of network administrators.

The SolarWinds Network Performance Monitor is primarily an SNMP bandwidth monitoring but it can do a lot more. At its core, the product offers comprehensive fault monitoring and performance management using SNMP and it is thereby compatible with most equipment. The tool’s NetPath feature lets you view the critical network path between any two monitored points on your network, In addition, it can also auto-generate intelligent network maps.

SolarWinds NPM - Network Summary

Other strengths of the product include advanced alerting and the tool’s PerfStack performance analysis dashboard. Another exclusive feature is the Network Insights functionality which allows for complex device monitoring. The tool can also monitor Software Defined Networks (SDN) and has built-in Cisco ACI support as well the ability to monitor wireless networks and to generate network performance baselines.

The SolarWinds Network Performance Monitor has a rather simple pricing structure. Licensing is based on the number of monitored elements. Five licensing tiers are available for 100, 250, 500, 2000, and unlimited elements at prices ranging from $2 955 to $32 525, including the first year of maintenance. If you’d rather give the tool a test run before committing to a purchase, a free, element-unlimited 30-day trial version can be obtained.

2. Nagios Core

There are two versions of Nagios available. There’s the free and open-source Nagios Core and then there’s the paid Nagios XI. Both share the same underlying engine but the similarity stops there. Right now, let’s have a look at Nagios Core, the open-source monitoring system that runs on the Linux operating system. This is a completely modular system with the actual monitoring engine—the actual Nagios core—at its core. This powerful engine is complemented by dozens of available plugins that can be downloaded to add functionality to the system, with each plugin adding some features to the core.

Nagios Core Screenshot

The modular approach goes well beyond the tool’s back end, though. The tool’s front-end is just as modular, if not more. Different community-developed front-end options are also available for download. The Nagios Core, the plugins and the front end combine and make for a rather complete monitoring system. There is, however, a drawback to this modular concept, though. Setting up Nagios Core can turn out to be a challenging task. This is somewhat compensated by the community-based support that is available.

Paid Alternative: Nagios XI

Nagios XI is an enterprise-grade server and network monitoring software which provides comprehensive application, service, and network monitoring in a central solution. The product is a direct descendant of Nagios Core and it uses the same core engine. This product lets you monitor all mission-critical infrastructure components such as applications, services, operating systems, network protocols, systems metrics, and network infrastructure.

Nagios XI’s powerful dashboards provide at-a-glance access to powerful monitoring information and third-party data. Various views provide users with quick access to the information they find most useful. The tool’s GUI is highly customizable and its layout, design, and preferences can be modified on a per-user basis, giving your team members the flexibility they want.

Nagios XI Dashboard

Nagios XI is very easy to use, thanks to its integrated web-based configuration interface which lets administrators manage monitoring configuration, system settings, and more. The platform also offers configuration wizards to guide users through the process of monitoring new devices, services, and applications without having to understand complex monitoring concepts.

Nagios XI is available in a Standard Edition and an Enterprise Edition. The Enterprise Edition offers additional functionality and includes features designed to aid in large-scale configuration, forecasting, and scheduled reporting. Each license includes twelve months of maintenance and email support. Licensing is based on the number of monitoring hosts and starts at $1 995 for the Standard Edition and $3 495 for the Enterprise Edition. If you’d like to give the product a test run, a free 60-day trial version is available.

3. LibreNMS

LibreNMS is an open-source port of Observium, a very potent commercial network monitoring platform reviewed below. It is a full-featured network monitoring system that provides a wealth of features and device support. Among its best features is its auto-discovery engine which doesn’t only rely on SNMP to discover devices. It can automatically discover your entire network using CDP, FDP, LLDP, OSPF, BGP, SNMP and ARP. Talking about the tool’s automation features, it also has automatic updates so it will always stay current.

LibreNMS Screenshot

Another major feature of the product is its highly customizable alerting module. It is very flexible and it can send alert notifications using multiple technologies such as email, like most of its competitors but also IRC, slack, and more. If you’re a service provider or your organization bills back each department for their use of the network, you’ll appreciate the tool’s billing feature. It can generate bandwidth bills for segments of a network based on usage or transfer.

For larger networks and for distributed organizations, the distributed polling features of LibreNMS allow for horizontal scaling to grow with your network. A full API is also included, allowing one to manage, graph, and retrieve data from their installation. Finally, mobile apps for iPhone and Android are available, a rather unique feature with open-source tools.

Paid Alternative: Observium Professional

Observium is a low-maintenance monitoring platform with auto-discovery. It supports a wide range of device types, platforms and operating systems including, among others, Cisco, Windows, Linux, HP, Juniper, Dell, FreeBSD, Brocade, Netscaler, NetApp. I doubt that you can find a WAN router that’s not supported. The tool’s primary focus is providing a beautiful, intuitive, and simple yet powerful user interface showing the health and status of your network.

Observium Screenshot

Observium has more than just bandwidth monitoring. For instance, there’s an accounting system that will measure total monthly bandwidth usage in the 95th percentile or in total transferred bytes. It also has an alerting function with user-defined thresholds. Furthermore, this product integrates with other systems and can pull their information and display it within its interface.

Observium users love how easy it is to set up and how it almost configures itself. Although there doesn’t appear to be a download section on the publisher’s website, there are detailed installation instructions for several Linux distributions that do include the links to get the right package for each distribution. The instructions are very detailed and installing the software should be easy.

4. Icinga

Icinga is another excellent monitoring platform. It has a simple and clean user interface and, more importantly, a feature set that rivals some commercial products. Like most bandwidth monitoring platforms, this one uses SNMP to fetch and compute bandwidth utilization data from network devices. But one of the areas where this tool particularly stands out is its use of plugins. There are thousands of community-developed plugins that can perform various monitoring tasks, thereby extending the product’s functionality. And in the unlikely event that you couldn’t find the right plugin for your needs, you can write one yourself and contribute it to the community.

Icinga Screenshot - Tactical Overview

Alerting and notification are also among Icinga’s best features. Alerts are fully configurable in terms of what triggers them and how they are transmitted. The tool also features what is referred to as segmented alerting. This feature will let one send some alerts to one group of users and other alerts to different people. This is nice to have when you monitor different systems managed by different teams. It can ensure that alerts are transmitted only to the proper group to address them.

Paid Alternative: PRTG Network Monitor

The PRTG Network Monitor from Paessler AG is another great product. It is, at its base, an SNMP monitoring tool. However, thanks to a concept called sensors—a type of functionality plug-ins that are already built into the product—additional metrics can be monitored. There are about two hundred sensors available with the product. Installation speed is another strength of the product. According to Paessler, you can set it up in a couple of minutes. While it may not be that fast, it is indeed faster than most competitor’s thanks in part to the tool’s auto-discovery engine.

PRTG Dashboard - Datacenter Monitoring

PRTG is a feature-rich product that lets you choose between a native Windows enterprise console, an Ajax-based web interface and mobile apps for Android and iOS. Alerting and reporting are both excellent and the product boasts a wide range of reports that can be viewed as HTML or PDF or exported to CSV or XML to be processed externally.

PRTG is available in a free version which is limited to monitoring no more than 100 sensors. Each parameter you want to monitor counts as one sensor. For example, monitoring bandwidth on each interface of a 4-port router will use up 4 sensors and monitoring the CPU and memory on that same router will use up 2 more. Each additional sensor you install also counts. For more than 100 sensors—which you will most likely need—you’ll need a license. Their prices start at $1 600 for up to 500 sensors, including the first year of maintenance. A free 30-day trial version is also available.

Wrapping Up

Whether you choose to go towards an open-source or a closed-source monitoring tool is up to you. We’ve explained the differences between the two and described each type’s advantages and disadvantages. We’ve also reviewed some of the best free and open-source tools we could find and some commercial counterparts so you can see what’s available. Paid or free, we can easily recommend any of the tools we’ve just reviewed and the best for you is the one that best matches your specific needs.

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