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.

Extreme Networks - Extreme Networks (EXTR) delivers customer-driven enterprise networking solutions that create stronger connections with customers, partners, and employees.