Subbing

Subbing is a rapid-fire subnetting quiz app built for network engineers, students, and anyone preparing for CCNA, CompTIA Network+, or similar certifications.

QUESTIONS INCLUDES
• Network and broadcast addresses
• First and last usable hosts
• Subnet masks and wildcard masks
• Prefix lengths (/8 through /30)
• Usable and total host counts
• Is-host-in-subnet checks

THREE MODES
Competitive: 5-minute timer, all question types, mixed difficulty, free-form answers. Submit your score to the global leaderboard and see how you stack up.
Timed: 10-question sprint with a per-question countdown. Every second counts.
Just for Fun: no timer, unlimited questions, and step-by-step explanations after wrong answers. Great for learning.

FOUR DIFFICULTY LEVELS
Easy through Hard, or Mixed for a random challenge. Hard mode includes wider prefix ranges and wildcard masks.

MULTIPLE CHOICE OR FREE-FORM
Easier difficulties offer multiple-choice grids to help you get started. Medium and hard push you to type the answer from memory.

GLOBAL LEADERBOARD
Global competitive scores. Submit your display name and compete with the community.

REMOVE ADS
A one-time in-app purchase removes all banner ads permanently and supports development.

No account required. No login. Just questions and answers.