Free Monitor Tools
AppNeta – SpeedCheckr – A FREE Network speed monitoring tool.
Scrutinizer NetFlow Analyzer – A FREE version of Plixer’s very own Scrutinizer. Supports unlimited flows on unlimited routers or switches.
Denika Performance Trender – Amazing free SNMP trending tool based on MRTG. Keeps things easier than MRTG and provides high level summary reports.
Flowalyzer – Test and configure your Cisco NetFlow and sFlow sending devices with Flowalyzer.
Getif – A great SNMP MIB browser
Qcheck – This is a nifty utility for running response time, throughput and streaming tests.
STG – Realtime SNMP graphing utility. You need to know the MIB.
Wireshark – A packet analyzer that runs on Microsoft Windows and UNIX. One of the best values on the web.
Nmap – A free and open source network scanning utility for exploring the network or security auditing.
Zenmap Security Scanner GUI is also available for free, which makes Nmap easier for beginners and adds some features