Angry IP Scanner - Open-source and cross-platform network scanner designed to be fast and simple to use
whatmask - Whatmask is a small C program that will help you with network settings and subnet calculations.
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.
ipcalc - IP Calculator. ipcalc takes an IP address and netmask and calculates the resulting broadcast, network, Cisco wildcard mask, and host range. By giving a second netmask, you can design subnets and supernets....
Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
ship.sh - 🚢 🌊 A simple, handy network addressing multitool 🔎 with plenty of features.