Planning VLANs and subnets is one of those tasks that every network engineer does regularly, but rarely has a good tool for. Spreadsheets work, but they’re slow and error-prone. Dedicated tools are often paid or require installation.

So I built one: VLAN Planner – a free, browser-based tool that runs entirely in your browser with no account required.

What it does

• Plan subnets visually – enter a parent network, then add subnets row by row with VLAN ID, name, purpose, and gateway
• Overlap detection – highlights overlapping subnets and subnets outside the parent range in real time
• IPv4 and IPv6 – full support for both address families, including BigInt-based IPv6 math for 128-bit prefixes
• Subnet Calculator – built-in calculator for both IPv4 and IPv6 CIDR blocks (network address, broadcast, usable hosts, wildcard mask, address scope)
• CSV and PDF export – export your plan for documentation or sharing
• Auto-save – your work is saved to localStorage, so nothing is lost on page refresh

Why I built it

I was doing a network redesign at work and needed to plan 15+ VLANs across multiple sites. I opened a spreadsheet, started typing… and immediately remembered why I hate doing this in spreadsheets.

After a few hours of searching for a decent free tool and finding nothing that did exactly what I needed, I decided to build it myself over a weekend.

Try it

subnetplanner.net – free, no account, no ads.

Works best for:

• Home lab network planning
• Enterprise VLAN documentation
• Subnetting practice (CCNA/CCNP students)
• IPv6 addressing plans

Feedback and suggestions are welcome.