DCImanager - DCImanager is a platform for managing physical equipment. Connect any physical equipment to a single platform. Use the platform to manage your servers, switches, PDU as well as physical and virtual networks.
Fing - Discover which devices are connected to any Wi-Fi network, map devices, detect intruders, assess...
NetBox - NetBox is an open source web application designed to help manage and document computer networks. NetBox was developed specifically to address the needs of network and infrastructure engineers.
Angry IP Scanner - Open-source and cross-platform network scanner designed to be fast and simple to use
Opendcim - a free, web based Data Center Infrastructure Management application.
Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.