Network Monitoring Software covers a surprisingly wide gambit of software and functionality. Some software is focused purely on observation and tracking of monitoring network traffic, while others are more geared on response and awareness, with features that let you set alarms or even trigger scripts based on specific events, and still other pieces of software allow you to focus on the trends of traffic and network performance for sake of longer term adjustments and heuristics for hardware devices.
Whatever your needs may be there's likely a free, open-source option that can perfectly fit the bill. Every network should have at least one of these tools available; whether you're performing some in-depth troubleshooting and need a program with powerful data aggregation and graphing abilities to help pinpoint a problem device or application, or if you're tracking the traffic of several physical devices over several different network environments over time to watch for trends in your bandwidth needs or other statistics.
The interesting thing about Zabbix is that there is no enterprise level paid version, it's all completely open-source and completely free. They do offer some consulting and monitoring contracts, but the software itself is wide open! It's one of the most powerful open-source options in this realm and can handle most all of the standard NMS needs, plus some.
One prime advantage is that it has a particularly slick and intuitive interface, while also being exceptionally easy to install with compatibility across numerous systems and environments. On the flip side, some of its ability to aggregate and report information, and especially then exporting that information, could definitely be a bit stronger in their offering.
Available for Red Hat Enterprise Linux 5, 6 and 7, CentOS, Debian, Oracle Linux and Ubuntu 12.04 and 14.04
Download Link: http://www.zabbix.com/download.php
Observium is another offering with a really slick interface style to it. The charts and graphs are all readily available and organized in a beautifully intuitive fashion. This program pushes more into the realm of physical monitoring of devices and can even show where, geographically, systems are located and how they're communicating and passing traffic!
It uses a variety of methods for monitoring and does an excellent job of providing automatic discovery while still allowing manual additions. There are few NMS software packages that will do so much of the legwork for you and do it accurately!
Observium even has a cohesive web interface, meaning you have a lot less to worry about when it comes to accessing controls and viewing network status and statistics from anywhere you are. The software itself is, however, Linux-based aside from the web-based front-end. Observium does have a professional edition.
Available for Linx/Unix including Debian, RHEL, Ubuntu, CentOS 6 and 7.
Download Link: http://www.observium.org/docs/
Cacti is a little more particular in its purpose, and slightly more restricted – it does require a MySQL backend database and SNMP has to be installed and configured on agent devices for full functionality, in addition to Cacti itself requiring a PHP/Apache backbone.
Despite this, it's an extremely powerful but simple tool – it takes data, aggregates it, and presents it in just about any way or combination you can possibly want or imagine. If there's any need to see several sets of data side by side, to manipulate them, to draw in data from several other metrics that normally wouldn't even be relevant, Cacti can do it all. It's a tool that focuses primarily, if not almost exclusively, on trend tracking and graphical representations of data sets.
Available for Windows, Linux/Unix variations (Gentoo, Debian, Fedora and SUSE)
Download Link: http://www.cacti.net/download_cacti.php
Nagios is one of those programs that is an absolute rose but definitely has its thorns. It's an older software, meaning it's tried and true – it's extremely fast and incredibly reliable, but the learning curve for newcomers can easily be prohibitive.
It is similar to some other offerings in that it is immensely flexible – Nagios can track, monitor, and follow trends of almost any data that can be gathered from a network environment, and it's that same flexibility and wide-open capabilities that are both its strength and it's main drawback. A powerful piece of monitoring software that is not for the faint of heart. If nagios doesn't fit the bill, check out the best nagios alternatives for other options.
Available For RHEL, CentOS and Nagios for Windows using VMWare or Virtual PC virtual machines.
Download link: https://www.nagios.org/downloads/
Icinga is a program that gives some of the others, Zabbix especially, a run for its money but falters when it comes to intuitive setup and configuration. Icinga requires a good wealth of knowledge to know how to get it setup just right, but once you do it's among the Best open source NMS on the market. Of particular note is the unusual modularity of Icinga – the core software can be installed with just a few small commands, which is the easy part, and from there almost any other functionality, both standard NMS and beyond, can be added one by one.
The downside is that each one has to be installed and configured individually, and that coupled with documentation that isn't so great for quick setup, makes this another powerful tool that's challenging to put to use right away.
Available for Debian, Ubuntu, RHEL/CentOS, openSUSE, SLES, Gentoo, FreeBSD, ArchLinux and Icinga for Windows will require Vagrant and VirtualBox or Parallels Desktop, along with Ruby for Windows installed.
Download link: https://www.icinga.org/download/
Whatever program you choose you can take full advantage of the Open-Source nature of each, meaning that an attractive price-tag of ‘Free!' lets you try out all the different software options to see what works best for you and your monitoring needs. And you can rest easy knowing that the source code is fully available and heavily audited and monitored by the community, which helps reduce security concerns and prevent issues normally present from developer shortsightedness. Grab one of the above Free Open Source NMS software packages and give a whirl and see which one works Best for you and your needs.