Hi, On Sun, Jan 22, 2023 at 11:42:18PM -0500, Celejar wrote: > Shouldn't this be included somewhere prominently in the Debian > documentation, in the form of a Big Fat Warning that the standard > dual-stack condiguration used by Debian can cause serious breakage if > one's ISP doesn't support IPv6?
Not having IPv6 is not the problem. As you discovered later in this thread, your ISP is providing just enough IPv6 for your router to think it has a v6 block to hand out, but not enough that it actually works. It's a misconfiguration by your ISP and not something that any operating system's documentation needs to point out. They could also let you connect to them but make IPv4 not work, it's just that you'd notice that very quickly! If you don't have a global scope IPv6 address on any interface then at the point where your system is trying to decide what source address to use for some packets, it will not that any IPv6 source address to use. If there are IPv4 addresses to talk to then it will source from one of your IPv4 addresses, or else give an error. The change suggested here to gai.conf says to try IPv4 first, which is why it fixes things for you. I'm not sure but I think you may still have a bad time in the event that a DNS response included ONLY IPv6 addresses, because the need for a v6 source address would bypass gai.conf settings and then instead of getting an instant failure you'd again get the long timeout while your non-working IPv6 was used. But that is obviously an edge case here. Anyway, if the ISP can't fix the IPv6 and can't be convinced to stop advertising it even when it doesn't work, I think you'd be best off trying to disable radvd on the router. Failing that, disabling IPv6 on all your clients (check your phones too, as they will try IPv6 these days if they think it's available). Cheers, Andy -- https://bitfolk.com/ -- No-nonsense VPS hosting
