What an AAAA record is
An AAAA record maps a name to one IPv6 address. It does the same job as an A record, for the newer and much larger IPv6 address space. The name "AAAA" comes from the address being four times as long as an IPv4 address (128 bits against 32).
example.com. 300 IN AAAA 2606:2800:220:1:248:1893:25c8:1946Do you need one?
A site works with only an A record, because nearly every network can still reach IPv4. An AAAA record lets visitors on IPv6 networks, common on mobile carriers, connect directly.
Only publish an AAAA record if the server really answers on that address. Clients that have IPv6 try it first. If it is broken they fall back to IPv4 after a delay, and the site feels slow or fails for those visitors only.
Common AAAA record mistakes
- A record that outlived the server. The IPv4 address was moved and the AAAA record still points at the old machine.
- A firewall that only allows IPv4. Port 443 is open on the IPv4 address and closed on the IPv6 one.
- A web server not listening on IPv6. In nginx that is a missing
listen [::]:443line.
The symptom is the same each time: the site fails for some people and works for others. Test with curl -6 https://example.com.