With the PRTG Free Version, you will receive 100 Sensors that will never expire. Generally, 10 sensors would be needed for each of your network devices. Setting up a “lighter” monitoring environment is an option, such as via the use of a single SNMP sensor to monitor traffic or one ping sensor for monitoring availability.
PRTG license model is based on the number of sensors you will need to meet your requirements and expectations concerning your monitoring environment. Try the unlimited version of PRTG for 30-Days, at no cost, where you’ll still have access to 100 free sensors. The trial will help you determine the number of sensors you will need.