4 free network monitoring tools to keep you in the know

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When loading the Web interface for the first time, there is a short wizard that confirms that the pre-requisites and database connection are properly configured before loading the main dashboard. The first screen is the personal dashboard, which provides a general overview of the IT infrastructure with a list of hosts, system and host status. On a new installation this screen is largely blank with the exception of information related to the Zabbix server itself. This dashboard is customizable; you can add preferred graphs, maps and screens as you configure them.

Zabbix collects data in three different ways; by installing agents on a Linux/Windows host or by using a variety of protocols such as SNMP, ICMP, TCP and SSH. Basic network health information can also be collected over HTTP and SMTP. Zabbix can use auto-discovery network devices and also had the capability to perform low-level discovery. We started by configuring a discovery rule to map out our test network. The granularity of this configuration is very good and you can specify IP ranges, protocols and other criteria to determine how a network is mapped out. After a few minutes we started to see a list of devices, ranging from routers and printers to servers and desktops. The discovery provides a general network overview, but does not provide any in-depth information until you add the individual host/device to Web interface. We added several hosts using both the Zabbix agent for Linux and Windows, together with a few utilizing SNMP.

We installed the agents using a single command on our Linux hosts. There are some configuration options that can be set in the ‘zabbix_agentd.conf ‘configuration file, such as the server IP and server name along with other custom options. The agents can perform either passive checks, where certain data (memory use, disk space, bandwidth) is essentially polled from the Zabbix server, or active checks, where the agent retrieves a ‘to-do’ list from the server and sends update data to the server periodically. Installing as a Windows service is also fairly straightforward using an executable and making a few tweaks to a configuration file to let Windows know where the Zabbix server resides.

The Web interface is a bit complex and looks intimidating at first, but once you become a bit more familiar with the various screens and terminology we found it easy to navigate. We also wish the fonts and graphics were a bit more prominent as some of the information can be difficult to read. One of features we liked is the dynamic link history that shows which section you recently used, allowing you to quickly navigate back. The online user manual is comprehensive and up to date, and the Zabbix website has lots of comprehensive information on features, installation and configuration options.

Administrators can either use built-in templates or create their own triggers to build rules that send messages and/or perform commands when certain conditions are met. For instance, we created a rule that sent us a message when there was a general problem with one of the hosts and also restarted the agent on that host. Rules provide a lot of granularity and this was one of the few areas where we wish the online manual had a bit more detail on configuration options.

Most of the reporting is to the screen with the ability to print. The print option essentially displays what is on the screen minus the navigation header and other extraneous information. This is a not necessarily a bad configuration, but it does not make for the most elegant printouts. We would have liked to have seen some ‘save-as-PDF’ and export capabilities. That being said, the online reporting and graphs are excellent, with multiple customization options. As mentioned earlier, the custom graphs and screens can be added to the main dashboard and called up with a simple click.

Zabbix is all open source. There is no separate paid Enterprise version. This means all of the source code is open source and available, which should be attractive to both small and large enterprises. Although Zabbix does not offer a separate commercial version, commercial support contracts are available in five different levels ranging from ‘Bronze’ to ‘Enterprise’. Zabbix also offers other paid services such as integration, turnkey solutions and general consulting.


Initially created as a fork from Nagios in 2009, Icinga’s latest version has been developed per the vendor "free from the constraints of a fork." Version 2 sports a new rules-driven, object-based configuration format. Icinga is still open source under GPL and the current releases include Core and Web 1.11.x versions along with a 2.x version. Icinga can monitor devices in both Linux and Windows, but the server itself runs only on Linux. Since the 2.x Web GUI was still in beta, we installed the core server version 2.x and used the latest 1.1x version as the Web GUI.

Icinga has a modular design where you select the core server, your preferred GUI and add any desired plug-ins such as reporting and graphing tools. We installed the basic server using only two commands. Overall, we found the Icinga online documentation to be good; however, a quick start guide would have been helpful as there is no guidance from the get-go on which of the many configuration files needs to be tweaked, even for a basic installation.

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We determined that we needed either a MySQL or PostgreSQL database in order to run the Web interface; in addition Apache or NginX plus PHP are also required. There are a few steps involved in this install and configuration process, depending on how many incremental upgrade files are available for the Icinga 2 DB IDO module and also how the Web server is configured. We went through the list of commands and after a fair bit of trial and error we were able to access the Web GUI from a browser.

After logging in, a dashboard type overview is displayed with navigation organized into groups along the left, Icinga calls them ‘cronks’ with the main part of the screen used to display information. Along the top there is a section that provides an overview of the infrastructure using color coded counts with healthy hosts shown in green, warnings in yellow, critical problems in orange and hosts that are unavailable in red.

Icinga maximizes the use of most screens and even if the first impression is a bit cluttered, overall we found the navigation and organization of data to be intuitive. Many of the screens are list based, displaying information about hosts and host issues sorted by various criteria such as availability, length of down time or severity of the issue. Icinga provides the ability to sort each list ascending or descending on each column, something we found very helpful. Furthermore you can select which columns to display for each list on the fly, this provides a nice level of customization.

Icinga takes advantage of several common protocols for monitoring the network infrastructure, from simple PING commands to SNMP, POP3, HTTP and NNTP. Information can also be gathered from other devices such as temperature sensors and other network-accessible devices. Configuring which hosts to monitor and what to monitor is accomplished using the configuration files and the granularity to which you can customize this is overwhelming, the ‘Basic Monitoring’ section of the user manual runs 50 pages. Luckily, you can use templates and re-useable definitions to streamline this process.

For our environment we defined a few hosts by linking a name to the IP addresses and then added what is known as ‘check commands’. These are essentially protocol definitions such as PING and HTTP that instruct Icinga what to monitor for each host. You can then expand these configurations to include how often to query a host, when to escalate warnings and where to send email notifications of pending issues.

Configuration files are the core of Icinga; we counted 14 main files and some of these include additional files for more specific configurations. Some configuration files can be left with default values, but others must be configured specifically for the environment such as hosts, email addresses for notifications and enabling/disabling services used for host monitoring. The configuration files can be modified/created using an editor like VI or nano, but there are also configuration add-ons available plus third-party tools such as Chef and Puppet. In future releases Icinga will be adding the ability to configure via GUI, API as well as CLI, something that would be helpful for items that may require ongoing changes, such as changing host configurations.

Icinga provides native support for Graphite for graphing purposes and an Icinga Reporting module is available; it is based on the open source Jasper Reports.

There is no paid version of Icinga available, but there are several organizations worldwide that offer paid support at different levels. Icinga also hosts several camps every year where users, developers and sponsors get together to discuss best practices and further development goals of the product.


When selecting monitoring tools it is important to have a clear goal from the outset. Are you looking to just send a ping to each device every 15 minutes to make sure the device responds? Or, do you need more comprehensive information such as CPU, RAM, disk and bandwidth usage? Installing agents and configuring SNMP to access more advanced features should be a consideration as this can be a time-consuming task that may not be practical in larger organizations. A workable hybrid approach could be to install agents on critical devices that need deep-dive monitoring, while monitoring other devices in agent-less mode.

Perschke is the CEO of Arc Seven Technology, which offers managed web hosting and custom application development services. She can be reached at susan@arcseven.com.

This story, "4 free network monitoring tools to keep you in the know" was originally published by Network World.

Copyright © 2015 IDG Communications, Inc.

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