DNS & operations
Following a domain name to an address
A concise field guide to authoritative DNS, resolvers and record changes.
Two different roles
Authoritative DNS servers publish records for a zone. Recursive resolvers look up those records on behalf of clients and cache the answers. The resolver used by a laptop is usually not the authoritative server for the requested domain.
A and AAAA records
An A record associates a name with an IPv4 address. An AAAA record associates it with an IPv6 address. Publishing IPv6 is useful only when the service and firewall are configured to accept it correctly.
Why updates take time
Resolvers may keep an answer until its time to live expires. Negative answers can also be cached. Changing a record at the authoritative provider therefore does not instantly replace every cached answer.
Check from both ends
Inspect the authoritative answer and the answer returned by the client resolver. Then test the actual service at the resulting address. DNS resolution, a successful TCP connection and a valid HTTPS response are separate checks.