Subnet Trainer

Why this is not the Speed Test

The Subnetting Speed Test (one of the Games) already drills IPv4 arithmetic, and drills it well: network and broadcast addresses, first and last host, masks, prefixes, host counts, wildcards, smallest fit. Building a second drill for the same questions would only split your practice in half.

So this one asks what that one does not. Which address is which: given a block, is this the network, the broadcast, or something you can hand to a machine. Do these two need a router: the mistake where .70 and .200 look like neighbours and sit in different /26s. And IPv6, which had no practice anywhere on this site until now: address types, how many /64s fit in a /56, prefixes, and writing an address the short way.

On the IPv6 short form

There is one correct way to write an IPv6 address, and it is worth knowing rather than guessing: RFC 5952. Drop the leading zeros inside each group. Replace the longest run of all-zero groups with a single ::, and only once. If two runs tie for longest, compress the leftmost. A single zero group is written 0, not ::.

The drill checks against that rule, and generated addresses always have one unambiguous longest run, so there is never a second defensible answer.

How the score works

The same measure the Speed Test uses: Net CPM, correct answers per minute, where speed × accuracy = net is an identity rather than a weighting. It divides by the time you actually took, so finishing a quota early scores the faster rate you earned. A run needs at least 20 seconds and 4 answers before it counts towards a best. Nothing leaves your browser.