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A DNS lookup is the conceptual process by which a client finds appropriate resource records for a domain name, typically through iterative or recursive queries. Results are cached according to TTL to reduce latency. Security and error semantics such as NXDOMAIN and CNAME chains are also part of the model.
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A DNS lookup retrieves the resource records associated with a domain name. It combines resolvers, name servers, caches, and response codes so that names can be translated into usable network data.
The lookup model is part of the DNS architecture described in 1987 in RFC 1034 and RFC 1035 by P. Mockapetris. It emerged because HOSTS.TXT no longer scaled with the growing Internet: centralized maintenance became expensive, slow, and error-prone. DNS distributed the naming space, delegated responsibility to zones, and made iterative as well as recursive queries with local caches possible.
Think of a lookup as a tiered inquiry in a distributed directory. The resolver checks the cache first, then follows referrals to additional servers until an authoritative name server returns the needed record. A response may be a direct answer, a referral, a negative reply, or a CNAME continuation; TTL determines how long the result stays in cache.
The distributed naming space provides the data basis for resolving names to other resources.
The local intermediary accepts the request, checks the cache, and coordinates further steps.
Servers return authoritative answers or point to the next responsible place.
The usual target of a lookup is an IP address, although DNS can return other record types as well.
Cached answers remain valid only until their TTL expires, after which they must be resolved again.
The concept is useful for troubleshooting, domain migrations, mail routing, and security analysis. It explains why changes do not appear everywhere at once: caches and TTLs introduce delay, and CNAME chains or negative responses can slow diagnosis. Reliable conclusions require checking both the responsible answer source and the current cache state.
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