Every device on the internet has an IP address. For most of the internet’s history, those addresses followed the IPv4 format – four groups of numbers separated by dots, like 192.168.1.1. IPv4 supports about 4.3 billion unique addresses, which sounded like more than enough in 1981 when the protocol was designed.
It was not enough. The internet ran out of available IPv4 addresses years ago. IPv6 is the solution – a newer addressing scheme that supports a vastly larger address space, using 128-bit addresses written in hexadecimal like 2001:0db8:85a3:0000:0000:8a2e:0370:7334.
DNS maps domain names to IP addresses. When IPv6 arrived, DNS needed a new record type to store IPv6 addresses alongside the existing IPv4 records. That record type is the AAAA record.
A records vs AAAA records
A records map a domain name to an IPv4 address. When your domain has an A record pointing to 203.0.113.50, devices connecting over IPv4 use that record to find your server.
AAAA records (pronounced “quad-A”) map a domain name to an IPv6 address. When your domain has a AAAA record pointing to 2001:db8::1, devices connecting over IPv6 use that record.
The name “AAAA” comes from the fact that an IPv6 address is 128 bits – four times the length of a 32-bit IPv4 address stored in an A record.
A domain can have both an A record and a AAAA record simultaneously. Most modern websites that support IPv6 publish both. Clients that support IPv6 use the AAAA record. Clients that only support IPv4 use the A record. This dual-stack approach allows gradual IPv6 adoption without breaking anything for IPv4-only users.
You can look up both record types for any domain using SiteProbe’s DNS lookup tool. Select the AAAA record type to see whether a domain has IPv6 addresses configured.
How DNS resolution works for IPv6
When a device makes a DNS query, modern operating systems with IPv6 support query for both A and AAAA records simultaneously or in quick succession. The process:
- Your device sends a DNS query for
example.comrequesting AAAA records - If the domain has a AAAA record and your network supports IPv6, your device uses the IPv6 address
- If no AAAA record exists or your network does not support IPv6, the resolver falls back to the A record
- Your browser connects to whichever address was resolved
Most modern browsers and operating systems implement a strategy called Happy Eyeballs (RFC 8305) to handle the transition period smoothly. Happy Eyeballs attempts IPv6 and IPv4 connections nearly simultaneously, with a slight preference for IPv6, and uses whichever completes first. This prevents IPv6 connection delays from affecting page load time when IPv6 is available but slow.
What is Dynamic DNS (DDNS) and how does it relate to IPv6
Dynamic DNS (DDNS) is a service that automatically updates DNS records when your IP address changes. This is typically used for:
- Home servers and self-hosted services where the ISP assigns a dynamic IP that changes periodically
- IoT devices and remote access setups that need a consistent hostname despite changing IPs
- Development and testing environments that move between networks
With IPv4, DDNS has been widely used because residential ISPs often assign dynamic IPv4 addresses. You get a hostname like
myhome.dyndns.org
that always points to your current IP regardless of what that IP is, updated automatically by a client running on your router or device.
With IPv6, the situation is more complex. IPv6 addresses can be assigned through several mechanisms:
SLAAC (Stateless Address Autoconfiguration): Devices generate their own IPv6 address from the network prefix and their MAC address. The address is stable as long as you stay on the same network but changes when the prefix changes (which ISPs do periodically).
DHCPv6: The router assigns IPv6 addresses via DHCP, similar to IPv4. Addresses may be stable or dynamic depending on ISP policy.
Privacy extensions: Modern operating systems generate temporary random IPv6 addresses that change periodically to prevent tracking. These are used for outgoing connections but not typically for hosting services.
For hosting a service on a dynamic IPv6 address, DDNS works the same way as with IPv4 – a client monitors your current IPv6 address and updates the AAAA record automatically when it changes. Most DDNS providers support both A record updates (IPv4) and AAAA record updates (IPv6).
When you need AAAA records
Running a web server
If your web server has an IPv6 address and you want IPv6 clients to be able to connect using your domain name rather than the raw IPv6 address, you need a AAAA record. Without it, IPv6-only clients cannot resolve your domain.
IPv6-only clients are still a small minority of web traffic, but that share is growing. Large mobile networks in some countries assign IPv6-only addresses to mobile devices. Enterprise networks and ISPs are increasingly IPv6-native.
Email delivery
Mail servers increasingly use IPv6. If your mail server has an IPv6 address, publishing a AAAA record alongside the appropriate MX records allows other mail servers to deliver to you over IPv6. Some spam filtering systems also consider IPv6 configuration when evaluating sender reputation.
CDN and cloud services
Most major CDNs and cloud providers have native IPv6 support. When you point your domain to a CDN, they typically provide both A and AAAA records to add to your DNS configuration. Publishing both ensures optimal routing for all visitors regardless of their IP version. IPv6 also pairs well with modern protocols – HTTP/3 and QUIC are designed to work efficiently over both IPv4 and IPv6.
Government and enterprise requirements
Some government contracts and enterprise RFPs require IPv6 support as a condition of doing business. Publishing AAAA records is one of the visible signals of IPv6 readiness.
When you do not need AAAA records
If your hosting provider does not have IPv6 addresses assigned to its servers, there is nothing to put in a AAAA record. Publishing a AAAA record pointing to an address that does not have your server listening on it will cause connection failures for IPv6 clients.
If you are on shared hosting, check whether your hosting provider supports IPv6. Some do, some do not. If your provider gives you an IPv6 address for your account, publish a AAAA record. If they only provide an IPv4 address, stick with the A record.
How to set up AAAA records
Setting up a AAAA record is the same process as setting up an A record, just with the record type changed and an IPv6 address in the value field.
In most DNS management interfaces:
- Log into your DNS provider or registrar’s DNS management panel
- Find the option to add a new DNS record
- Set the record type to AAAA
- Set the name to your domain or subdomain (@ for the root domain, www for www, etc.)
- Enter your server’s IPv6 address in the value field
- Set an appropriate TTL (3600 is standard)
- Save
Your server’s IPv6 address is provided by your hosting provider. It typically looks like
2001:db8:1234:abcd::1
– eight groups of four hexadecimal digits, with consecutive groups of zeros sometimes collapsed to
::
.
After publishing the AAAA record, verify it is resolving correctly using SiteProbe’s DNS lookup tool. Select the AAAA record type and enter your domain. You should see the IPv6 address you configured returned in the results.
IPv6 address formats
IPv6 addresses have several equivalent representations. Your DNS record needs to use the correct format.
A full IPv6 address:
2001:0db8:0000:0000:0000:0000:0000:0001
Leading zeros within each group can be omitted:
2001:db8:0:0:0:0:0:1
One consecutive sequence of all-zero groups can be collapsed to
::
:
2001:db8::1
All three of these represent the same address. Most DNS management interfaces accept any valid IPv6 format and store it in a canonical form.
Troubleshooting AAAA record issues
IPv6 connectivity problems
If you have published a AAAA record but some visitors cannot reach your site, the problem may be IPv6 connectivity on their end rather than your DNS configuration. Not all networks support IPv6. ISPs in some regions still provide IPv4-only connections.
As long as you also have a working A record, IPv4-only visitors will fall back to it automatically. A AAAA record that does not work should not break your site for IPv4 visitors – it will affect only visitors whose devices try IPv6 first and cannot reach your server on that protocol.
Wrong IPv6 address in the record
Unlike IPv4 where a wrong A record is usually obvious, IPv6 addresses are long and easy to mistype. Double check the full address character by character against what your hosting provider gave you. A single wrong hexadecimal digit sends traffic to the wrong address or nowhere at all.
Server not listening on IPv6
Publishing a AAAA record does not automatically make your server listen on IPv6. Your web server (Nginx, Apache) needs to be configured to listen on the IPv6 address in addition to the IPv4 address. If your server is only listening on IPv4, IPv6 clients will get connection refused errors even though DNS resolves correctly. If you recently migrated your site and are setting up IPv6 for the first time, see How to migrate WordPress to another hosting provider for the full DNS configuration steps involved in a server move.
In Nginx, ensure your listen directives include IPv6:
nginx
listen 80;
listen [::]:80;
listen 443 ssl;
listen [::]:443 ssl;Firewall blocking IPv6
Your server’s firewall needs to allow traffic on IPv6 interfaces just as it does for IPv4. If you added firewall rules for your IPv4 address but not for the IPv6 interface, traffic arriving via IPv6 will be dropped silently.
Checking IPv6 DNS with SiteProbe
SiteProbe’s DNS lookup tool supports all DNS record types including AAAA. Use it to:
- Verify your AAAA record is published and returns the correct IPv6 address
- Check whether a domain you are connecting to has IPv6 support
- Compare A and AAAA records to see both IPv4 and IPv6 addresses for a domain
- Verify that your AAAA record has propagated after publishing or updating it
Summary
AAAA records are the DNS record type that maps domain names to IPv6 addresses, the same role that A records play for IPv4. A domain can have both simultaneously, allowing both IPv4 and IPv6 clients to connect using the same hostname. Dynamic DNS (DDNS) works with AAAA records the same way it works with A records – automatically updating the record when your IPv6 address changes. You need a AAAA record if your server has an IPv6 address and you want IPv6 clients to resolve your domain. Without a AAAA record, IPv6-only clients cannot reach your site by domain name. Verify your AAAA records are configured correctly using tools.hostney.com/dns.