An AAAA record associates an owner name with one IPv6 address. The four
letters are the record mnemonic, not a count of addresses.
Purpose and type code
IANA registers AAAA as type code 28
[1]. Its RDATA
is one 128-bit IPv6 address in network byte order
[2]. More than one AAAA
record at an owner forms an RRset of IPv6 addresses.
Presentation format
www.example.com. 300 IN AAAA 2001:db8::10Zone files use the normal textual representation of an IPv6 address. The
documentation prefix 2001:db8::/32 is reserved for examples and should not be
used as a production destination.
Owner-name and coexistence rules
AAAA and A RRsets may coexist at the same owner so clients can discover both IPv6 and IPv4 destinations. AAAA can also coexist with other ordinary data, but not at a CNAME owner; a CNAME alias cannot carry other ordinary RRsets [3].
Query transport and answer address family are independent. A resolver can ask for AAAA over IPv4 or ask for A over IPv6 [2].
Caching and changes
AAAA and A are separate RRsets with separate answers and potentially different TTLs. Removing a broken AAAA record does not immediately erase copies already held in recursive or client caches. Plan overlap and rollback for both address families.
Security and operational limits
Publishing AAAA advertises an IPv6 destination; it does not prove that routing, firewalls, load balancers, TLS, or the application work over IPv6. A partially working IPv6 path can produce failures even when IPv4 remains healthy.
DNSSEC may authenticate the RRset but does not test IPv6 reachability or encrypt the query.
Verify
Query AAAA explicitly and capture the source, answers, TTL, and time. Then test the service over IPv6 rather than assuming that a DNS answer means the path is usable. Verify A separately when the service is dual-stack.
Next step
Read the CNAME record reference before replacing direct address records with an alias.