DNS record types
A and AAAA records
Map a hostname directly to an IPv4 or IPv6 address and know when both record types should exist.
8 minute lesson
An A record maps a name to an IPv4 address. An AAAA record maps a name to an IPv6 address.
For example:
www.example.com. 300 IN A 192.0.2.40
www.example.com. 300 IN AAAA 2001:db8::40The owner name is www.example.com, 300 is the TTL, and the values are addresses. A record cannot contain https://, a port, or a URL path. DNS gets the client to a host; the application protocol handles the rest.
A name can have several A or AAAA records. DNS can return all of them, but that alone is not a health check. Unless another service monitors and removes failed addresses, clients may still receive an unreachable destination.
Modern clients can request both record types and choose a working route based on their network. Publish an AAAA record only when the service, firewall, TLS configuration, and return path really work over IPv6. A broken IPv6 path can make a healthy IPv4 website appear unreliable.
Check the two families separately:
dig A www.example.com +short
dig AAAA www.example.com +short
curl -4 https://www.example.com/
curl -6 https://www.example.com/The curl checks test more than DNS: they also require routing, a listening service, and valid HTTPS. This separation helps explain why a correct DNS answer does not guarantee a working page.
Your action is to query both address types for a hostname you use. If both exist, test both connection families and record whether the DNS and HTTP evidence agree.
Lesson completed