Negative caching
Negative caching is a resolver's practice of remembering that a DNS query returned no answer -- either NXDOMAIN (the name doesn't exist) or NOERROR with an empty answer (the name exists but not for the requested record type) -- so it can return that same negative result without re-querying authoritative servers. RFC 2308 defines how long a negative answer may be cached: the TTL comes from the minimum value in the zone's SOA record, not the TTL of the (nonexistent) record itself. This matters in practice because a misconfigured or not-yet-propagated DNS record can keep failing for resolvers that cached the earlier NXDOMAIN, even after the correct record is published, until that negative-cache TTL expires.
By AdminKit team, Netbase JSC · Updated