What do DNS A and AAAA records show?¶
DNS uses different record types to answer different questions. A and AAAA records link a name to an IP address that a device can try to use.
A record: IPv4¶
An A record associates a domain name or hostname with an IPv4 address.
AAAA record: IPv6¶
A AAAA record, usually said as “quad A”, associates a name with an IPv6 address.
A domain may publish A records, AAAA records or both. A device that supports both address types can decide which route to try.
Read a representative answer¶
shop.example. 300 IN A 198.51.100.20
shop.example. 300 IN AAAA 2001:db8:20::25
| Part | Meaning |
|---|---|
shop.example. | The exact name answered |
300 | The time to live in seconds, allowing the answer to be cached for up to five minutes |
IN | The internet DNS class |
A or AAAA | Whether the answer supplies an IPv4 or IPv6 address |
| Final value | An address that software can try to use |
This answer establishes that these routes were published or supplied at the relevant observation point. It does not show which route the device selected or whether any connection succeeded.
One name may have several records¶
A service can publish several A or AAAA records at once. This may spread traffic between servers, provide resilience or direct users to different locations.
The records can also change when a service moves, replaces infrastructure or changes provider. A current lookup may therefore differ from the answer available at the event time.
One address may serve many names¶
An A or AAAA record does not mean the address is dedicated to that domain. Several domain names can share one IP address through hosting, cloud or content-delivery infrastructure.
How to use the result¶
An A or AAAA record shows a published route from a name to an address. Record:
- the exact name queried;
- the record type;
- every address returned;
- the date and time of the lookup;
- the resolver or service used; and
- the record's time to live, if available.
For an earlier event, look for contemporary DNS, network or platform records rather than relying only on today's answer.
Operational takeaway
Preserve the exact name, record type, every returned address, TTL, timestamp and resolver. An A or AAAA answer supplies a possible route; a separate connection or application record is needed to show what happened next.
