Network monitoring with Cacti

There are a few powerful tools available, such as MRTG, the Multi Router Traffic Grapher, but setting them up can be an exercise in frustration for first-time users. By contrast, Cacti, a graphing program for network statistics, is designed to be easy for relatively inexperienced systems administrators to use, while at the same time being powerful enough to be used in complex networks.

Cacti's Web site describes the software as:
a complete network graphing solution designed to harness the power of
RRDTool's data storage and graphing functionality. Cacti provides a fast poller, advanced graph templating, multiple data acquisition methods, and user management features out of the box. All of this is wrapped in an intuitive, easy-to-use interface...