Subnetting Practice
CCNA-style subnetting drills: seeded random questions on hosts, masks, wildcards and address ranges — graded instantly, with every set shareable by URL.
Your practice set (seed 20261016, 10 questions)
Type an answer, press Check — grading happens right here in your browser.
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What single CIDR block covers 134.218.64.0 - 134.218.127.255?
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What is the broadcast address of 48.185.69.205/16?
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What is the network address of 130.228.200.22/20?
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What is the dotted subnet mask for /25?
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How many usable hosts are in a /16 network?
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Which prefix length corresponds to the subnet mask 255.255.254.0?
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What is the wildcard mask for a /22 block?
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What single CIDR block covers 57.109.64.0 - 57.109.127.255?
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What is the broadcast address of 203.139.46.49/28?
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What is the network address of 63.15.64.104/25?
Answers are not stored or sent anywhere — nothing leaves your browser.
How to practice
- Keep the date-based seed for the daily challenge, or type any number to get a fresh set.
- Answer each question and press Check — you get instant right/wrong feedback plus a worked explanation.
- Missed one? Read why, then regenerate with the same seed to retry the identical set until it sticks.
To assign homework, submit the form once and copy the resulting URL: everyone who opens it sees the same questions because the seed fully determines them.
Worked example: usable hosts in a /26
A /26 mask (255.255.255.192, wildcard 0.0.0.63) leaves 6 bits for hosts. Those 6 bits give 26 = 64 addresses, but two of them are reserved: the network address itself (all host bits 0) and the broadcast address (all host bits 1). That leaves 64 − 2 = 62 usable hosts.
The edge cases matter for exams: a /31 point-to-point link keeps both addresses usable (2 hosts per RFC 3021), and a /32 host route has exactly 1. This drill includes those prefixes occasionally so the exceptions stay fresh.
Related references
- Subnet cheat sheet — every mask from /16 to /32 on one printable page.
- IPv4 subnet calculator — check any network, broadcast or wildcard answer step by step.
- VLSM calculator — practice splitting a block by host requirements.
- Deep-dive the common masks: /24 subnet mask, /26 subnet mask, /30 subnet mask.
Frequently asked questions
How does this subnetting practice tool work?
Every question type works without an account, and you can generate new sets by changing the seed. Answers are graded in the browser.
What does the seed do?
The seed is the starting value for a deterministic random generator. Seed 20260823 always produces exactly the same questions as any other visit to that URL, which makes shareable assignments possible. The default seed is today's date, so the untouched page is a shared daily challenge.
Are my answers graded on the server?
No. The server renders the questions into the page, but grading happens entirely in your browser using the same generator code. Your answers never leave your device.