Names, answers & caches
Domains & DNS
Learn what a domain name identifies, why DNS caching matters, and how to connect web records without disrupting mail.
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DNS TTL
A DNS answer can outlive a change at its source. Follow one resolver cache—not a global propagation clock.
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Domain name
A domain names a place in DNS. It is neither the complete URL nor the site files or hosting account.
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Connect a domain to a website
Connect web DNS safely without disrupting existing mail: check delegation, stage the site, change only needed records and verify.
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DNS resolution
Trace cold and cached DNS lookups, distinguish referrals from answers, and see why NXDOMAIN, NODATA and an HTTP response are different outcomes.
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Authoritative nameserver
Learn how authoritative nameservers answer for DNS zones and why registrar delegation must point to the zone you edit.
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Recursive DNS resolver
Understand recursive DNS resolvers, cache hits and misses, negative caching, and why cached data is not a global clock.
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DNS A and AAAA records
Compare DNS A and AAAA records by address family, check both sets independently and avoid assuming IPv6 always works.
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CNAME record
See how a DNS CNAME aliases a hostname to another name and why ordinary records cannot share that alias owner.
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MX record
Understand MX targets and lower-number mail preference, independent of website A/AAAA records and mail authentication TXT.
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Change a DNS record safely
Rehearse a single web A-record change, inspect the protected zone data, compare two resolver caches and practice a rollback that does not erase cached answers.
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A DNS change is not visible
Diagnose an invisible DNS change by separating wrong-zone edits, delegation, cached positive or negative answers, and record type.
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Start with a domain name and DNS TTL. When connecting a domain, identify its authoritative provider, preserve mail records, and verify the destination before switching.