MRTG stands for Multi Router Traffic Grapher. It tracks the traffic load on network links.  The monitoring tool provides a LIVE visual representation of the traffic by generating HTML pages that contains PNG images. It reads the traffic counters of the routers through the Perl script. It uses a highly portable SNMP implementation which is required to install external SNMP package. In addition, it monitors system load, login sessions, modem availability, etc. The MRTG can visualize the two or more data sources combined into a single graph.