Zenoss Core - Zenoss (Zenoss Core) is an open source application, server and network management platform based on...
Zabbix - Track, record, alert and visualize performance and availability of IT resources
LANState - LANState - Network Mapper and Device Monitor
NetVizura NetFlow Analyzer - NetFlow Analyzer is a solution for bandwidth monitoring and traffic analysis. It helps with traffic investigation, analysis and reporting
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
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.