> Every time I look at a [long] ipv6 address my brain goes “fack this”.

I do get that but I also get 'There are so many I could have all I wanted ... or I could if any of our fiber ISPs would support it, that is'

I finally clicked when I worked out it was 2^64 subnets . You have a common prefix of you /48, which isn’t much longer than an ipv4 address - especially as it seems everything is 2001::/16, which means you basically have to remember a 32 bit network prefix just like 12.45.67.8/32.

That becomes 2001:0c2d:4308::/48 instead

After that you just need to remember the subnet number and the host number. If you remember 12.45.67.8 maps to 192.168.13.7 you might have

2001:0c2d:4308:13::7

So subnet “13” and host “7”

It’s not much different to remebering 12.45.67.8>192.168.13.7