About this tool
Network, broadcast, host range, mask and wildcard for an IPv4 subnet, and splitting it into smaller ones. This tool works entirely in your browser. Nothing you type is sent anywhere.
Free to use, no sign-up. We don’t log or store what you look up.
Review your firewall rules too
Paste a config from 12 firewall platforms — plus switches, Wi-Fi, NAC, Azure NSG, NetScaler, F5 and more — and get a graded review with fix commands, mapped to 16 standards. The config never leaves your browser.
Start free See a sample report