Tools
Free Network Tools
Built and maintained by our network practice, free for anyone to use. The calculators and generators run in your browser and need no account; the quiz takes a free one, so your progress is saved.
Revising for CCNA or Network+, planning a real network or tidying a spreadsheet of subnets: start here. When the plan outgrows a calculator, our network and identity design work picks up from there. Something wrong or missing? toolfeedback@greywellcyber.com.
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Subnet Calculator
IPv4 and IPv6. Network, broadcast, host range, mask and wildcard at a glance.
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VLSM Planner
Split one IPv4 block into named subnets of different sizes, largest first, with the spare space shown.
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Networking and Subnetting Quiz
Practice questions across twelve topics, from subnetting maths to OT risk. Free with an account, so your progress is saved.
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Password Generator
Random passwords or random word passphrases from the EFF list of 7,776 words. Made in your browser.
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Route Summariser
Turn a list of IPv4 networks into the fewest summary routes that cover them exactly.
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Security Headers Checker
Read the HTTP security headers a public website sends, with a plain note on each.
Guides
- IPv4 Network Design : Zoning, the DMZ, /24 standards, address containers and when not to use them.
- IPv6 Design : Why the /64 is fixed, /127 on links, nibble boundaries, SLAAC or DHCPv6, and PMTUD.