On Mon, Jul 06, 2026 at 08:53:59 +0100, Chris Green wrote: > It's a single host at that address/domain. As I said it's a VPS and > the isbd.biz domain is mine and has A and AAAA records pointing solely > at the VPS. > > As pointed out elsewhere the issue is caused by isbd.biz having an > IPV6 address as well as an IPV4 one.
There's still a mystery here -- why do you get different results when you connect to the IPv6 address instead of the IPv4 address? You'd probably have to investigate the server side to figure out why those two addresses have different behaviors. It could be that you're running two separate instances of sshd. I don't think that's the most likely answer, but it's a possibility. You could also be using a Match block in your sshd_config, which disables key authentication (either globally or for specific users) when the local or remote address is IPv6. This would be a weird setup, but I can't rule it out. It could also be something else that I can't currently imagine.
