Zabbix - Track, record, alert and visualize performance and availability of IT resources
Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.
NetVizura NetFlow Analyzer - NetFlow Analyzer is a solution for bandwidth monitoring and traffic analysis. It helps with traffic investigation, analysis and reporting
tcpdump - tcpdump is a common packet analyzer that runs under the command line.
netcat - Netcat is a featured networking utility which reads and writes data across network connections...
Easy-IP - IPAM and DNS for Telecoms