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Tech & ITDNS (Domain Name System)
By Sitraka Forler · Lecturer, Durham Business SchoolUpdated 13 September 2026 About this site
The internet's address book: it translates domain names into IP addresses.
DNS stores records for each domain: A and AAAA give its IPv4 and IPv6 addresses (Internet Protocol versions 4 and 6), CNAME (canonical name) points one name at another, and MX (mail exchange) names its mail servers. DNS servers cache each answer for the record's TTL (time to live), so after a change some users may get the old address until it expires, which is why a moved site can work for you but not a colleague.
Example
# its IPv4 address(es) dig example.com A +short # its IPv6 address(es) dig example.com AAAA +short # full answer: the 2nd column is the seconds left in the cache (at most the TTL) dig example.com A +noall +answer # the same lookup, also built into Windows nslookup example.com