Paessler PRTG 100 Network Monitor

Paessler PRTG 100 Network Monitor (100% Discount)

Get license here: https://shop.paessler.com/shop/free_license/?showkey=1&download=1
Note: For the first 30 days you can try PRTG with unlimited sensors. 
After this time period is over, you'll be able to continue using 100 sensors for free forever!