6.2. Rejected Queries and Malformed Responses

6.2 Rejected Queries and Malformed Responses

Some authoritative nameservers respond with REJECTED or NOTIMP when queried for an RR type they do not recognize. At least one authoritative resolver produces a malformed response (with the QR (Query/Response) bit set to "0") when queried for unknown RR types. Per [RFC1034], the correct response RCODE for unknown RR types is 0 ("No error condition").