The Dude - MikroTik is a Latvian company which was founded in 1996 to develop routers and wireless ISP systems. MikroTik now provides hardware and software for Internet connectivity in most of the countries around the world.
Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
Pandora FMS - Pandora FMS: Opensource monitoring software
Fing - Discover which devices are connected to any Wi-Fi network, map devices, detect intruders, assess...
OpenNMS - Project home page of OpenNMS - a java based network managememnt platform developed under the Open Source model
SoftPerfect Network Scanner - Powerful multipurpose network administration tool for Windows and macOS