Open Source Monitoring System for performance and availability.
Nagios network monitoring software is enterprise server monitoring
free netflow analyzer
Enhanced Apache Server Status page - for one or multiple servers
Monitoring and reporting web gui for Bacula
Zenoss - Intelligent IT Operations Management
PHP-based looking glass for Cisco, Juniper & Zebra/Quagga routers
OPTOSS Next Gen Network Management System (NG-NetMS)
inventory, asset management network monitoring and backup appliance
Track your ARP/MAC table changes and so much more
Open source tool to monitor your servers and websites
Open Source SIEM
Netflow visualisation and investigation tool
DOCSIS network management
Network Intrusion Detection and Full Packet Capture System