Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

← Challenges easy

subnet review

Playing as a guest — your score won't be saved. Log in to keep it.

Someone worked out a device's subnet by hand. Exactly one line is wrong, and any line after it carries on from the mistake. Click the first wrong line.

Found it! points.

Not quite — line was the first mistake.

+ XP

Next → Play again Back to Challenges