From device discovery to visibility into systems, networks, and traffic flows, these free open source monitoring tools have you covered

In the real estate world, the mantra is location, location, location. In the network and server administration world, the mantra is visibility, visibility, visibility. If you don't know what your network and servers are doing at every second of the day, you're flying blind. Sooner or later, you're going to meet with disaster.

Fortunately, many good tools, both commercial and open source, are available to shine much-needed light into your environment. Because good and free always beat good and costly, I've compiled a list of my favorite open source tools that prove their worth day in and day out in networks of any size. From network and server monitoring to trending, graphing, and even switch and router configuration backups, these utilities will see you through.









Too often, IT administrators think they can't color outside the lines. Whether we're dealing with a custom application or an "unsupported" piece of hardware, many of us believe that if a monitoring tool can't handle it immediately, it can't be handled. That's simply not the case, and with a little bit of elbow grease, almost anything can be monitored, cataloged, and made more visible.

An example might be a custom application with a database back end, like a Web store or an internal finance application. Management wants to see pretty graphs and charts depicting usage data in some form or another. If you're using, say, Cacti already, you have several ways to bring this data into the fold, such as constructing a simple Perl or PHP script to run queries on the database and pass counts back to Cacti or even an SNMP call to the database server using private MIBs (management information bases). It can be done, and it can generally be done easily.

If it's unsupported hardware, as long as it speaks SNMP, you can most likely get at the data you need, though it may take a little research. Once you have the right MIBs to query, you can then use that information to write or adapt plug-ins to collect that data. In many cases, you can even integrate your cloud services into this monitoring by using standard SNMP on those instances, or by using an API provided by your cloud vendor. Just because you have cloud services doesn’t mean you should trust all your monitoring to your cloud provider. The provider doesn’t know your application and service stack as well as you do.

Getting most of these tools running usually isn't much of a challenge. They typically have packages available to download for most popular Linux distributions, if they aren't already in the package list. In some cases, they may come preconfigured as a virtual server. Configuring and tweaking the tools can take quite a while depending on the size of the infrastructure, but getting them going initially is usually a cinch. At the very least, they’re worth a test-drive.

No matter which of these tools you use to keep tabs on your infrastructure, it will essentially provide the equivalent of at least one more IT admin -- one that can't necessarily fix anything, but one that watches everything, 24/7/365. The up-front time investment is well worth the effort, no matter which way you cut it. Be sure to run a small set of autonomous monitoring tools on another server, watching the main monitoring server. This is a case where it's always best to ensure the watcher is being watched.

This is an article I just read here, wondering why Capsa Free is not included, haha, I decided to add it here, really a useful tool that every IT admin can't miss.