example.com. 3600 IN AAAA 2606:2800:21f:cb07:6820:80da:af6b:8b2c
An AAAA record (“quad-A”) is the IPv6 counterpart of the A record: it maps a hostname to a 128-bit IPv6 address. The name comes from the address being four times as long as an IPv4 address.
Dual stack
Most sites publish both A and AAAA records. Clients that have IPv6 connectivity use the Happy Eyeballs algorithm (RFC 8305): they start an IPv6 connection first and fall back to IPv4 within a few hundred milliseconds if it is slow. That’s why a broken AAAA record often goes unnoticed — and why it should still be fixed.
Checklist
- Publish AAAA records only if the service really answers on that IPv6 address.
- Add a PTR record for mail servers’ IPv6 addresses, just as for IPv4.
- Firewalls are often configured separately for IPv6; test both families.
Frequently asked questions
- Do I need an AAAA record?
- Not strictly, but IPv6 now carries a large share of traffic. Publishing AAAA records lets IPv6 users connect directly, without passing through carrier NAT.
- Why is my site slow for some users after adding AAAA?
- If the IPv6 path is broken, clients wait before falling back to IPv4. Make sure the server listens on IPv6 and the firewall allows it.