Keep Tabs on Network Services with Nagios, Pt. 2 - page 2
Get to Know Your Configs
Nagios, again, can run anything you ask it to. This includes, for example, scripts that use snmpwalk to grab statistics from SNMP-enabled devices. A really neat use of Nagios is for network security purposes. You can configure a check that polls all of your routers and grabs their ARP table to run every few minutes. If you know roughly how many hosts you have, the number of entries shouldn't surprise you. When this number increases significantly, it could indicate some malicious activity is taking place on the network.
Security monitoring is a big deal. We don't recommend that you trust Nagios with the task of host security, but it can be useful for paging you when certain conditions are found true. Ideally, you'd want to write a script that checks a samhain database and notifies you if anything severe happens to be amiss. A useful plugin for secondary host monitoring, which runs chkrootkit, does exist. Chkrootkit can perform some pretty advanced checks, and it stays up to date with the latest tricks that malware employ. Chkrootkit is very resource intensive, but nonetheless useful to run once per day, along side your usual file integrity monitoring solution.
Temperature monitoring cannot be left out. There exists some very fancy, a.k.a. expensive, environment monitoring solutions for your data center. Nagios to the rescue. Plugins are available for Nagios that support many stand-alone temperature probes. A popular probe, TempTrax, is a very inexpensive solution for temperature monitoring.
A Nagios writeup wouldn't be complete without mentioning its reporting mechanisms. Nagios produces trend reports that are very accurate. For example, if Nagios was not running, or if logs from a certain time period mysteriously go missing, these times get reported as "undetermined." Many people use Nagios to report on SLA compliance to their clients.
Last but not least, we feel that the community deserves mention as well. One contributed add-on in particular, APAN, is extremely valuable. The Advanced Performance Addon for Nagios provides a Nagios-integrated Web page that displays RRD graphs. Now you can view your RRD graphs of network usage, load, etc all in one interface. There are also more generic ones, Like NagiosGrapher, that will generate graphs of all your Nagios data.
The graphing capabilities above promote Nagios to the level of "capable of providing a complete monitoring solution." Both the ease of configuration and the flexibility inherent in the Nagios design have made Nagios synonymous with data center monitoring. So what are you waiting for?
This article first appeared on Enterprise Networking Planet, a JupiterWeb site.