The sentence for 2345:0425:2CA1:0000:0000:0567:5673:23b5 is “How silently the linear strips unsettle the new time beyond new mean where inland overcasts desegregate.” I’m not sure that’s really that much easier to remember than the raw number.

Testing it with IPv4:

• 0.0.0.0 - Crimson hearths always wobble.
• 0.0.0.1 - Crimson hearths always return.
• 0.1.1.0 - Crimson pelicans wildly wobble.
• 255.0.0.0 - Endless hearths always wobble.

It’s probably four lists, 255 words each: adjective, noun, adverb, verb. Then each is associated with a number.

Then I tested it for the IPv6 version. In all tests, the IP used was 0000:0000:0000:0000:0000:0000:$IP_ending, and the resulting sentence was "The new times take now beneath the new time while new times take $sentence_ending. Here’s how it turned out:

Apparently the digits are split three by three; this is surprising because IPv6 has 32 digits, the division isn’t even and odds are some position gets only two digits. Each list likely has 16³=4096 words, but the same list is reused in multiple positions, that’s why “the new time” appears four times if all digits are zero.

All that said, this is probably useless. A IPv6 number is not something you remember, it’s something you store and copy and paste.