A modern, browser-based Variable Length Subnet Masking (VLSM) Calculator designed to quickly generate efficient IP subnetting tables from a CIDR block and subnet requirements.

🛠 Built with HTML, CSS, and vanilla JavaScript. No frameworks. No build tools. Just fast and clean subnetting.

• 📥 Accepts a base CIDR block (e.g. 172.16.0.0 and mask or prefix).
• 🧮 Calculates subnets dynamically based on number of required hosts.
• ➕➖ Add/remove subnet inputs on the fly.
• 📋 Displays clean, subnetting table.
• 🕊 Spreadsheet copy 'n paste friendly.

git clone https://github.com/safesploitOrg/vlsm-calculator.git cd vlsm-calculator

# Just double-click index.html

Or serve with Python:

python3 -m http.server 8000 # Then visit: http://localhost:8000

VLSM allows efficient IP address allocation by letting each subnet use a different prefix length depending on the number of hosts. This tool helps visualise and plan VLSM schemes interactively.

GitHub: @safesploitOrg
Original Author: @JCPedroza