Alternatives to: PRTG Network Monitor

LibreNMS is a free and Open Source network monitoring system offering comprehensive features and extensive device support.

OmniVista 8770 Network Management System: A unified, all-in-one solution for managing Alcatel-Lucent Enterprise communication networks.

The OmniVista 2500 Network Management System provides comprehensive tools for managing and monitoring converged campus networks and data centers, improving efficiency and providing valuable insights.

SmokePing is a powerful and flexible network monitoring tool that provides real-time visualization of network latency and packet loss.

WatchYourLAN is a lightweight network IP scanner with a web GUI for monitoring hosts and receiving notifications.