← DNS RecordsRecord Type / Address
AAAA Record
Maps a hostname to an IPv6 address. Required for dual-stack deployments as the internet transitions away from IPv4 exhaustion.
Overview
IPv6 Address Record
The AAAA record (sometimes called "quad-A") maps a hostname to a 128-bit IPv6 address. The name comes from the fact that IPv6 is 4× the bit-width of IPv4 — hence four As instead of one.
Most modern deployments publish both A and AAAA records — a configuration called dual-stack. When a resolver returns both, clients use the Happy Eyeballs algorithm (RFC 8305): they race IPv6 and IPv4 connections, preferring IPv6 but falling back to IPv4 within ~250ms if IPv6 fails. Publishing AAAA records costs nothing and benefits users on IPv6-capable networks.
- IPv6 addresses are 128-bit, written as 8 groups of 4 hex digits separated by colons
::compresses consecutive zero groups (e.g.,2001:db8::1)- Publish both A and AAAA — Happy Eyeballs picks the best at connection time
- Reverse DNS for IPv6 uses
ip6.arpawith nibble format - Mobile networks (especially in Asia and developing markets) are often IPv6-only
; Syntax
; Name [TTL] IN AAAA IPv6-address
; Zone apex (dual-stack with A)
@ 3600 IN A 203.0.113.42
@ 3600 IN AAAA 2001:db8::1
; Subdomain
www 3600 IN AAAA 2001:db8::1
; Full (uncompressed) notation
@ IN AAAA 2001:0db8:0000:0000:0000:0000:0000:0001
; Compressed notation (same address)
@ IN AAAA 2001:db8::1
; IPv6 loopback
; ::1 (equivalent to 127.0.0.1)
Check IPv6 Connectivity FirstBefore publishing AAAA records, verify your server actually listens on its IPv6 address and that your ISP routes IPv6 to it. A AAAA record that points to an unreachable address causes Happy Eyeballs delays for all IPv6-capable clients.
Diagnostics
Querying AAAA Records
Look up AAAA record
# Query AAAA record
dig thedns.guru AAAA +short
# Query both A and AAAA
dig thedns.guru A +short
dig thedns.guru AAAA +short
# Check if dual-stack is configured
dig thedns.guru ANY +short 2>/dev/null
Test IPv6 reachability
# Ping via IPv6
ping6 thedns.guru
# or
ping -6 thedns.guru
# curl over IPv6 explicitly
curl -6 https://thedns.guru
# Check your own IPv6 address
curl -6 https://ifconfig.co
IPv6 reverse DNS (PTR)
# Reverse lookup for IPv6
# 2001:db8::1 →
# 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0
# .0.0.0.0.0.0.0.8.b.d.0.1.0.0.2
# .ip6.arpa
dig -x 2001:db8::1 +short
# Or use host:
host 2001:db8::1
Verify Happy Eyeballs behavior
# Observe which address is used
curl -v https://thedns.guru 2>&1 \
| grep "Connected to"
# Force IPv4
curl -4 https://thedns.guru
# Force IPv6
curl -6 https://thedns.guru
# traceroute via IPv6
traceroute6 thedns.guru