The monitored device(s) must be equipped with SNMP Version 1, 2c or 3 (i.e. an SNMP compatible software must be installed on the device). SNMP must be enabled on the device and the machine running PRTG must be allowed access to the SNMP interface.
PRTG Traffic Grapher is an easy to use Windows software for monitoring and classifying bandwidth usage. It provides system administrators with live readings and long-term usage trends for their network devices. The most common usage is bandwidth usage monitoring, but you can also monitor many other aspects of your network like memory and CPU utilizations.