Practice
Drill it until it's automatic.
Reading is how you learn it; this is how you keep it. Everything here scores itself, explains the answer, and remembers what you got wrong.
Objective 1.6
Subnetting generator
Unlimited random problems — network, broadcast, range, host count, wildcard, prefix, VLSM — with a timer, a streak, and the binary worked out when you want it.
Appendix CFlashcards
173 cards covering every number in the guide: ports, administrative distances, timers, multicast groups, DSCP values. Cards you miss come back sooner.