LANState - LANState - Network Mapper and Device Monitor
Zenoss Core - Zenoss (Zenoss Core) is an open source application, server and network management platform based on...
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
Opsview Atom - Monitor everything. Integrate anything. Scale anywhere.
Shinken - Nagios compatible monitoring framework, written in Python
Ipsentry - Ipsentry is a comprehensive network performance management and monitoring system that provides real-time visibility and analysis of network performance across all layers of the OSI model.