About this tool
Every prefix from /0 to /32 with its netmask, wildcard mask and host count. 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