Which DNS server caches information from authoritative servers?

• A. Non-Authoritative DNS Server.
• B. Authoritative DNS Server.
• C. Primary DNS Server.
• D. Secondary DNS Server.

Answer: (A)

Caching of DNS responses is done by non-authoritative (recursive) resolvers. When a client asks for a domain, the recursive resolver fetches the answer by querying the root, then the appropriate top-level domain servers, and finally the authoritative server for that domain. It then stores the returned data in its cache for the time-to-live (TTL) specified by the authoritative source. This means subsequent requests for the same domain can be answered quickly from the cache without re-contacting the authoritative servers, until the TTL expires.

Authoritative servers hold and serve the definitive zone data and are not primarily about caching for general client queries. Primary and secondary servers describe the master/slave setup for a zone on authoritative servers, not the caching layer used to accelerate client lookups.