Essential SNMP

Chapter 13. 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 graphical 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 ...