Use MRTG to monitor bandwidth

In ”An introduction to SNMP” I have explained how SNMP protocol works and how use it; but what are the softwares that use SNMP to monitor network bandwith? HP Openview, Ciscoworks, MRTG are some examples. In this article I will explain how monitor Cisco Switches/Routers bandwith under a Linux machine using a free open source tool: MRTG. The Multi Router Traffic Grapher (MRTG) is a tool to monitor the traffic load on network links. MRTG generates HTML pages containing PNG images which provide a LIVE visual representation of this traffic. MRTG consists of a Perl script which uses SNMP to read the traffic counters [...]