Subnet Driller - CCNA Practice

About this app

An offline subnetting quiz for CCNA, Network+, and other certification candidates. Questions are randomly generated, answers are deterministic, and every calculation is hand-verified. It drills the "magic number" / block-size method I memorized before my own exams: built for speed and repetition. Features: - Built-in block-size ("magic number") reference, one tap away - Five question types: network address, broadcast, first and last usable host, usable host count - Multiple choice or written answers - or a mix of both - SESSION and TOTAL counters, plus a per-type accuracy breakdown - Optional daily practice reminder - Fully offline - no accounts, ads, tracking, or subscriptions - Shamelessly vibe coded using Fable 5; the subnet math lives in its own package and is hand-verified for accuracy About me: I'm a working network engineer and active CCNA, living in Arizona, USA. Questions, feedback, or bug reports? I read and reply to every email personally. Subnet Driller is an independent study tool, not affiliated with, endorsed by, or sponsored by Cisco Systems, Inc. or CompTIA, Inc. CCNA and Network+ are trademarks of their respective owners.

Fixed: if your device region uses a comma as the decimal separator — Norwegian, German, French, Portuguese and many others — you could not type an IP address at all, because the number pad has no period key. Commas now become dots as you type. Regions that use non-Latin numerals (Arabic, Persian, Hindi) now work too. Thank you to the person who wrote in about this — please keep the reports coming.

Momentum comes from crawler snapshots for the tracked storefront. “Viral growth signal” means unusually fast recent rating gains; it is an indicator, not download data.

1. First observed Sep 4, 2026 · 7:44 AM Free