IT shops have a critical responsibility to continuously monitor their environments to ensure that things are in working order and that there is resource capacity to meet business needs. Infrastructure performance is a core part of the services that run the business, and performance problems can plague IT departments and be difficult to nail down. Fortunately, a number of free tools are available that will monitor your network’s performance and help identify looming bottlenecks before they become an issue.

Over the years, I’ve used all five of the apps I’m highlighting here. That said, while I’ve used the first four quite a bit, I didn’t use Observium for very long. I can’t recall the reason, but I do know that it didn’t have anything to do with what I thought of the product; it’s actually pretty impressive.

Note: This article is also available as a photo gallery.

1: Multi Router Traffic Grapher (MRTG)

MRTG is the granddaddy of free network monitoring tools and provides basic but extremely useful information. Like all the tools featured here, MRTG gathers information using SNMP and then displays the trends that are inherent in the data. In Figure A, you can see a daily view of a router being monitored by MRTG. Figure B shows a graph displaying the information that has been gathered for the past year. This is the real power in these tools — they provide you with the data you need to make good decisions about your services and infrastructure.

Figure A

A look at an MRTG daily graph

Figure B

Use the yearly graph for long-term planning.

2: Cacti

First, a little background. RRDTool is a utility that was created by the same person who developed MRTG. RRDTool is intended to be a general purpose “high performance data logging and graphing system for time series data.” Basically, if you need to measure something over time, RRDTool is your friend.

So what does this have to do with Cacti? RRDTool by itself isn’t all that useful. There still needs to be some data collection mechanism in the background that RRDTool can use to create its visualizations. Cacti is intended to be a front-end system for RRDTool. It uses a MySQL database to store all the information that RRDTool needs to create graphs. Cacti allows you to create data sources (generally SNMP connections to monitored devices), gathers data from those devices, allows you to group graphs from like systems, enables you to manage user permissions to the monitored data, and much more.

As with MRTG, Cacti provides you with multiple time periods for viewing historical information. In Figure C, you can see that Cacti does a great job of displaying trending information in graph form. On the left-hand side of the display, see how Cacti allows you to group graphs to make things easier to find.

Cacti can take a bit of work to set up from scratch. You can accelerate the deployment by paying a small fee to download a fully preconfigured virtual machine from JumpBox.

Figure C

Cacti makes it easy to manage a lot of graphs

3: PRTG (10 sensors free)

Available from a company called Paessler, PRTG (which stands for Paessler Router Traffic Grapher) offers a quick way to begin monitoring a lot of network devices without requiring a lot of setup. PRTG also allows you to monitor other key systems, such as Exchange, SQL, VMware, and Windows, through the use of Windows Management Instrumentation (WMI) and connections to vCenter and ESX/ESXi hosts.

I recently provided an overview of PRTG 9, the latest version of the monitoring product. That overview contains a number of screenshots of the tool. Last year, fellow TechRepublic blogger Wally Bahny reviewed an older version of PRTG. His article also includes a number of screenshots.

PRTG isn’t completely free, though. You can deploy a free edition, but it’s limited. You get only 10 sensors. In PRTG, a sensor is an individual monitoring element. You would use one sensor to monitor disk space, another one to monitor RAM usage, another one to monitor total bandwidth usage, and so forth. You can quickly rack up hundreds or thousands of sensors. While this might sound like a sneaky way to charge you more money, the fact is that you get a great deal of choice over exactly what you’d like to monitor.

4: Spiceworks

Spiceworks has been around for quite a while. It’s an all-in-one tool that “bundles network monitoring, helpdesk, UPS power management, RFQ, PC inventory tools, an online community, and much more.” Spiceworks started as a network inventory and helpdesk system. It’s ad supported and completely free. Users can join a large community of IT practitioners to help find solutions to problems. As of this writing, Spiceworks says it supports close to 1.8 million IT pros. The product installs quickly on a Windows machine.

One significant module in Spiceworks allows users to monitor network and system health. In Figure D, you can see a page from Spiceworks that shows the overall health of various classes of devices.

Figure D

Spiceworks is free and easy to install.

5: Observium

From Observium’s site: “Observium is an autodiscovering PHP/MySQL/SNMP based network monitoring [tool], which includes support for a wide range of network hardware and operating systems, including Cisco, Linux, FreeBSD, Juniper, Brocade, Foundry, HP and many more.”

I really like Observium. It provides a lot of information in a way that makes it easy to consume. If you’re looking for a network monitoring tool, download and play with Observium — it’s free.

In Figure E, notice how Observium puts all the critical information front and center. You can see both current and historical information in an easy-to-read format.

Figure E

The Observium bandwidth graphs screen

Other tools?

Have you had a good experience with some of the tools discussed here? What other network monitoring apps would you add to this list?