Network Device Monitor is an excellent and free tool used to monitor real time health and performance of any SNMP (v1, v2, v3) based network device whether routers, switches, firewall or servers by configuring different thresholds. The installation and configuration is straight forward and offer variety of options meanwhile installing the product.
This free utility is designed with the ability to monitor more than just network status, availability, bandwidth and errors. NDM has a cool desktop dashboard that sends up a bat signal when device is in trouble or not performing up to par and includes the support for devices from all major manufacturers. The three options for choosing what to monitor provides you great flexibility and choices, built in Universal Device Poller (UDP), creating your own UDPs, or select it from Thwack online community. For me, the best practice is to create your own Poller or choose from Thwack instead of built in Poller. Network Device Monitor collects real time data associated with object identifiers (OIDs) and can retrieve data for nearly any conceivable network metric.
The best part of this free tool is Management Information Base - MIB compiler’s presence, which could help you load MIBs provided by your hardware or software manufacturer.
Handicapped to monitor just one device on network, still this tool become very handy to monitor the most critical device on the network and when the cost is in question.