Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
ManageEngine OpManager - Monitors routers, switches, firewalls, load-balancers, wireless LAN controllers, servers, VMs, printers, storage devices, and everything that has an IP and is connected to the network.
Angry IP Scanner - Open-source and cross-platform network scanner designed to be fast and simple to use
Cisco ACI - Application Centric Infrastructure (ACI) simplifies, optimizes, and accelerates the application deployment lifecycle in next-generation data centers and clouds.
Advanced IP Scanner - Advanced IP Scanner shows all network devices, gives you access to shared folders, and can even remotely switch computers off. Download it Free.
Device42 - Automatically maintain an up-to-date inventory of your physical, virtual, and cloud servers and containers, network components, software/services/applications, and their inter-relationships and inter-dependencies.