What is the difference between an A record and an AAAA record?

An A record maps a hostname to an IPv4 address. An AAAA record maps a hostname to an IPv6 address. A dual-stack hostname can publish both.

Can a DNS resolver reached over IPv4 return an IPv6 address?

Yes. A client can contact a resolver over IPv4 and receive an AAAA record containing an IPv6 address. Connecting to that destination over IPv6 still requires an end-to-end IPv6-routable path.

How does IPv6 reverse DNS work with PTR records and ip6.arpa?

A PTR record maps an IP address to a domain name. For IPv6, the address is represented as dot-separated hexadecimal digits in reverse order under the ip6.arpa domain.

Why can a dual-stack hostname fail when it has both A and AAAA records?

A hostname can resolve to an IPv6 address even when no end-to-end IPv6-routable path exists between client and destination. AWS describes this as a common dual-stack misconfiguration.

/section

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