In which an obscure conundrum is exposed
Some time ago someone reported issues accessing cpan.catalyst.net.nz a little peculiar and puzzling at the time, but we put it down to some weird DNS cache issues and moved on.
Turns out the problem is a DNS one, though not what we were thinking at the time:
$ host -t aaaa mail.catalyst.net.nz mail.catalyst.net.nz has IPv6 address 2404:130:0:10::40:0 2404:130:0:10::40:0 == 2404:0130:0000:0010:0000:0000:0040:0000 $ echo $((0x24)).$((0x04)).$((0x01)).$((0x30)) 220.127.116.11
So somewhere, some crappy device is getting a bunch of bytes back when it asks DNS for the address of something, and then it's taking the first four of them and calling that the IP address.
Kudos to David Clarke for spotting the actual problem.