Hi shoen,
Thank you for you answer.
I take some time to read the posts on this forum but I’m not able to know if their problems are related to mine.
All of them are about IPv6 but most of them are linked to a problem of configuration.
There is a request to change how Let’s Encrypt behave in this post Prefer IPv4 for validation when ACME client requests are IPv4. But I’m not sure that the proposal is correct.
The "Ipv6 address returns 404, ipv4 is good, but failed to verify the domain " (Ipv6 address returns 404, ipv4 is good, but failed to verify the domain) topic sound closer to my issue. But I do not understand the conclusion. Moreover, it seems that in this use case the user is able to configure the network has he want but this is not my case.
First of all, I would like clarify one point. I cannot force the box to use only IPv4 and I cannot change the DNS configuration of the access provider (owner of the box). The DNS returns two IP addresses (one IPv4 and another IPv6) because the network support both versions.
All the applications in Internet behave fine with my DNS configuration. As far as know, only Let’s Encrypt has a problem with that. For example I’m able to reach the server from my web browser and ssllabs.com (https://www.ssllabs.com/ssltest/) is able to get the certificates of the server.
My understanding of the current IPv6 specification is that the Internet applications have to prefer IPv6 but try IPv4 if IPv6 failed. This situation is mainly due to the fact that we have to live with an Internet mixing IPv4 and IPv6 computers.
This is exactly my situation. The box support IPv6 and IPv4. The box itself can be reach in IPv6 but the network behind is IPv4.
So according to the requested service, it is possible to use IPv4 or IPv6. In my case HTTP (80) and HTTPS (443) use IPv4 but the box itself is able to do some other stuff in IPv6.
Best Regards,
Vincent.