DNS AAAA Record

What is a AAAA Record?

A DNS AAAA record (also called a "quad-A" record) maps a domain name to an IPv6 address. While the A record handles IPv4 addresses (32-bit), the AAAA record handles the much larger IPv6 address space (128-bit). The name "AAAA" comes from the fact that IPv6 addresses are four times the size of IPv4 addresses.

As the internet transitions from IPv4 to IPv6 due to IPv4 address exhaustion, AAAA records have become increasingly important. Major websites, CDNs, and cloud providers now publish AAAA records alongside their A records to support dual-stack connectivity. This ensures that clients on IPv6-only networks can still reach these services.

When a DNS resolver queries for a domain, it typically requests both A and AAAA records simultaneously. If the client supports IPv6 and an AAAA record is available, the connection may be established over IPv6. Modern operating systems implement the "Happy Eyeballs" algorithm (RFC 8305) to quickly determine whether to use IPv4 or IPv6 for the best performance.

Syntax & Examples

The syntax of a DNS AAAA record follows the standard format:

example.com.    3600    IN    AAAA    2001:0db8:85a3:0000:0000:8a2e:0370:7334

The fields are: domain name (example.com.), TTL in seconds (3600), class (IN for Internet), record type (AAAA), and the IPv6 address. IPv6 addresses use eight groups of four hexadecimal digits separated by colons. Leading zeros can be omitted, and consecutive groups of zeros can be replaced with '::':

example.com.    3600    IN    AAAA    2001:db8:85a3::8a2e:370:7334

How to Query AAAA Records

To query AAAA records using dig, run: dig example.com AAAA. For concise output, use: dig +short example.com AAAA. To query a specific DNS server: dig @8.8.8.8 example.com AAAA. You can also check both A and AAAA records together: dig example.com ANY (though some servers restrict ANY queries).

With nslookup, use: nslookup -type=AAAA example.com. On Windows PowerShell: Resolve-DnsName -Name example.com -Type AAAA. To verify IPv6 connectivity end-to-end, you can use: ping6 example.com on Linux/macOS or ping -6 example.com on Windows. If no AAAA record is returned, the domain does not support IPv6.

Related Record Types

Frequently Asked Questions

What is a DNS AAAA record?

A DNS AAAA record maps a domain name to an IPv6 address, just as an A record maps to an IPv4 address. The name 'AAAA' (quad-A) reflects that IPv6 addresses are 128 bits long, four times the 32-bit length of IPv4 addresses used in A records.

Why is it called AAAA instead of A6?

The name AAAA was chosen because IPv6 addresses are four times longer than IPv4 addresses (128 bits vs. 32 bits). An earlier record type called A6 (defined in RFC 2874) was proposed as a more complex alternative, but it was deprecated in favor of the simpler AAAA record type due to implementation complexity.

Do I need both A and AAAA records?

It is recommended to have both A and AAAA records for maximum compatibility. This dual-stack approach ensures your domain is reachable from both IPv4-only and IPv6-only networks. If you only have an A record, IPv6-only clients may not be able to reach your site unless DNS64/NAT64 is available.

How do I check if a domain supports IPv6?

Run 'dig example.com AAAA' or 'nslookup -type=AAAA example.com' to check for AAAA records. If the query returns an IPv6 address, the domain supports IPv6. You can also use online tools like ip.now.to's DNS Lookup tool to query AAAA records for any domain.

Can AAAA records be used with CDNs?

Yes, major CDN providers like Cloudflare, AWS CloudFront, and Akamai fully support AAAA records. When you enable IPv6 on your CDN, it automatically provisions AAAA records pointing to the CDN's IPv6 edge servers, allowing IPv6 clients to connect directly to the nearest edge node.