Slash: Subnetting Practice
iOS Universel / Education
Slash drills the magic-number method until you can solve any subnet in seconds.
Open the Practice tab and you get random exam-style questions: find the network, the broadcast, the first or last usable host. Type your answer directly or pick from four options — both modes build the method differently, one through recall and one through recognition.
Get it wrong? Slash walks the magic-number method step by step, shows the full subnet (network, first host, last host, broadcast, next network), and gives you a "Quick Way" shortcut tailored to that question.
Right Neighborhood detection: if you typed the network when asked for the first host, Slash sees you got the math right and only got the wrong field. It tells you instantly — so the next time, you fix the mistake, not the math.
THE MAGIC-NUMBER METHOD
The fastest way to subnet by hand. Memorize one row of eight numbers (128, 64, 32, 16, 8, 4, 2, 1) and you can derive every mask, block size, and subnet boundary on a CCNA exam in under 30 seconds. Tap the table icon in the Practice header for the magic-box grid — the same one you'd scribble on the laminated sheet at Pearson VUE.
PROGRESS THAT EARNS, NOT GUILTS
Track total accuracy and per-question-type performance. Unlock milestones for first correct, first cross-octet, first /30, and total counts. Earn the You're Ready badge once you've cleared 50 answers at 90% accuracy with cross-octet and /30 questions in the bag. No streak guilt, no daily nag — just a clear signal of where you stand.
WHAT'S IN IT
• Practice tab — four question types, mixed text input and multiple choice
• Cheat Sheet — magic-box grid one tap away, from any question
• Calculator tab — the original Slash, still there for ad-hoc lookups
• First-run intro that walks the paper-and-pencil method with a worked example
• Hint button — surfaces the magic number for the current question
• "Quick Way" shortcut explanations on every reveal
• Cisco-style paste in the calculator (paste an interface config, it auto-splits)
• /31 honors RFC 3021. /32 handled. IPv6 mode in the calculator.
• Reset stats anytime in Settings
WHO MADE IT
Built by a CCNA who passed using this exact method. Slash is one focused thing: the magic-number method, drilled until your fingers know it, with native iOS polish and a cheat sheet you can write at the testing center.
WHAT IT WON'T DO
• No accounts, no sign-in, no telemetry.
• No network calls — fully offline. Verify with Airplane Mode.
• No third-party SDKs, ads, or trackers. Not now, not ever.
• No subscription. Free, the whole thing.
Privacy: Slash collects no data. Details at https://tylerdix.github.io/slash-site/#privacy
Questions or feature requests via the Support URL.
Quoi de neuf dans la dernière version ?
Slash is now a subnetting study companion, not just a calculator. And it's free.
NEW
• Practice — random questions: find network, broadcast, first/last usable host
• Cheat Sheet — the magic-box grid you write at the start of a CCNA exam, one tap away from any question
• First-run intro: the paper-and-pencil method with a worked example
• Hint button: the magic number for the current question + a link to the full cheat sheet
• Progress tracking, per-type accuracy, milestones, and the You're Ready badge
• Multi-choice mode mirroring the exam
• Reset practice stats anytime in Settings
CALCULATOR UPDATES
• "Next Network" row — see where the next subnet of the same size starts (great for VLSM planning)
• Cleaner default view: Network, First Host, Last Host, Broadcast, Next Network, Mask. Wildcard, Hosts, and Binary tucked into a "More details" fold