Subnet Workbench

A modern, browser-only network engineering toolkit. Inspired by davidc.net's classic Visual Subnet Calculator, modernized with IPv6, ACL/wildcard tooling, range→CIDR summarization, VLSM planning, and overlap checks.

Everything runs client-side. No tracking, no backend.

URL: https://jeakob.github.io/subnet-workbench/

Tools

• Visual Subnet Calculator — IPv4 split/join with notes & color-coding. The Separate action carves any subnet out of its parent plan into its own top-level network (the original allocation stays visible, dimmed, so the parent plan still reflects what's been carved out).

• IPv6 Subnet Calculator — prefix splitting, hex breakdown, EUI-64 helper

• CIDR ↔ Mask — instant two-way conversion + binary view

• Wildcard / ACL Builder — Cisco inverse mask + ready-to-paste ACL lines

• IP-in-Subnet Checker — does this address belong here?

• Subnet Compare — overlap, containment, adjacency

• Range → CIDR — smallest CIDR aggregation of an arbitrary IP range

• VLSM Planner — input host requirements, get an optimal allocation table

• Summarise — paste a list of prefixes (CIDR, IP+mask, ranges, IPv6) and get:

  • the single supernet (smallest covering CIDR), with exact-vs-over-coverage flag and waste count
  • an optimal aggregation — the minimal disjoint CIDR set that covers exactly the union (merges adjacent and overlapping inputs)
  • overlap detection and common-leading-bits analysis
  • Cisco IOS snippets — summary route, aggregated static routes, and ip prefix-list output
  • IPv6 support with the equivalent ipv6 route snippet

Features

• 100% client-side — your inputs never leave the browser
• Dark and light themes, with an adjustable accent color via the Tweaks panel
• Shareable URL state for visual subnet layouts (bookmark or send a link)
• Keyboard-friendly inputs; CIDR shorthand and subnet-mask entry both supported
• No build step — plain HTML, CSS, and JSX-via-Babel

Deploy on GitHub Pages

1. Push this repo to GitHub.
2. In the repo: Settings → Pages → Build and deployment → Source = GitHub Actions.
3. Push to main (or run the workflow manually). The included .github/workflows/deploy.yml builds and deploys automatically.

The workflow aliases Subnet Calculator.html to index.html so the app loads at the site root.

Local dev

Just open Subnet Calculator.html in a browser. Everything is static.

License

MIT