Change MAC Address - A powerful and simple tool for changing the MAC address of a network adapter.
Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Eusing Free IP Scanner - Free IP Scanner: a very fast IP scanner and port scanner.
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).
Angry IP Scanner - Open-source and cross-platform network scanner designed to be fast and simple to use