Subnet Mask Match
Sixty seconds of pure recall: turn a /prefix into its dotted-decimal mask — and sometimes the other way round. This is the table every network engineer knows cold.
How to get faster
You only ever need eight numbers: 128, 192, 224, 240, 248, 252, 254, 255. A mask is just that sequence walking across four octets. /24 fills three octets exactly; every prefix past /24 takes the next value in the list — /25 is 128, /26 is 192, /27 is 224, and so on. Learn the eight, and you know all 32.
Reference: subnet mask cheat sheet · what is a subnet mask · full IP & subnet reference.
More games
Subnetting Sprint
Network, broadcast, hosts and masks against the clock.
Play →60 secondsPort Number Rush
Match services to their well-known TCP/UDP ports.
Play →Speed is practice. Skill is the rack.
These drills build the recall speed the CCNA exam demands. The job demands more — configuring real routers and switches until it is second nature. That is what we teach in Ahmedabad, on real Cisco hardware.