Cisco Network Assistant - Cisco Network Assistant simplifies wired and wireless network management, and provides critical product information using Cisco Active Advisor.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
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).
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.
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.
Nagios - Complete monitoring and alerting for servers, switches, applications, and services