Zabbix - Track, record, alert and visualize performance and availability of IT resources
Cisco Network Assistant - Cisco Network Assistant simplifies wired and wireless network management, and provides critical product information using Cisco Active Advisor.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
Technitium MAC Address Changer - Technitium MAC Address Changer (TMAC) is a freeware utility to instantly change or spoof MAC Address of any network card (NIC).
Prometheus - An open-source systems monitoring and alerting toolkit.
Axence netTools - Axence netTools is completely free of charge, both for home and commercial use – all you have to do is to register. A tool for professionals – and others.