Chapter 12. MRTG


The Multi Router Traffic Grapher (MRTG) is a freely available and fully configurable trend analysis tool that's easy to configure and use. It's a surprisingly small, lightweight package because it doesn't implement a heavyweight user interface. Instead, it generates graphs in the form of GIF or PNG images; these graphs are embedded in standard HTML pages. Therefore, you can view MRTG's output using any web browser and even make its reports visible across your network by using a web server.

Although MRTG is best at displaying usage graphs for router interfaces, it can be configured to graph things like memory usage, load average, and disk usage on server equipment. MRTG is particularly useful for determining when something "peaks out" for an extended period of time, which indicates that you have a capacity problem and need to upgrade. For example, you might find that your T1 interface is maxed out during your peak business hours and you need to upgrade to a bigger circuit, or you might find that you need to add more memory to a server. Likewise, MRTG may let you know that your network connections are operating at a fraction of the available bandwidth and that you can therefore eliminate a few T1 circuits and reduce your telecommunications costs.

Many sites that use MRTG use its default graphing capabilities for capacity planning and provisioning. MRTG doesn't provide the fine-grained statistical tools you need to calculate baseline information or project when your network will need to be upgraded. However, it can be a very useful tool for businesses that don't have the resources to purchase a full-fledged trend analysis package. Baselines and projections are invaluable, but MRTG's graphs can give you similar behavior at a glance; your eyes are very good at spotting typical behavior and trends, even if they can't give you the statistical analysis that managers might like.

MRTG has many options that allow you to customize how it operates. It is beyond the scope of this chapter to discuss every option; instead, we will discuss how to install MRTG and use its default graphing capabilities. We'll also outline how you can configure MRTG to gather system information from a server.

It's important to understand that MRTG is not an NMS solution. Although its graphing capabilities make it look superficially like an NMS, it's really a simple polling engine that's very clever about the output it generates. It performs the same get functions that an NMS would, but its job isn't problem detection and resolution. It doesn't have a facility for generating alarms or processing traps, nor does it have the ability to set objects. It's simply designed to provide a graphical view of how your network is performing. If you're interested in an open source NMS package, you should investigate OpenNMS (http://www.opennms.org). This and other open source NMS packages are described in Appendix G.




Essential SNMP
Essential SNMP, Second Edition
ISBN: 0596008406
EAN: 2147483647
Year: 2003
Pages: 165

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