Windows error 9504 (DNS_ERROR_RCODE): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: A DNS response contains an RCODE failure that must be decoded for the specific server result.

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DNS_ERROR_NO_PACKET	DNS_ERROR_UNSECURE_PACKET

DNS_ERROR_RCODE

The generic status is only a wrapper

DNS_ERROR_RCODE says that the DNS operation failed because of a response code, but it does not identify which RCODE caused the failure. The useful diagnosis is the value in the DNS response header, possibly extended by EDNS information in an OPT record. Treating every occurrence as NXDOMAIN or SERVFAIL discards the server’s actual explanation.

Standard RCODEs distinguish format errors, server failure, nonexistent names, unsupported operations, refusal, update prerequisites, authorization, and other conditions. Extended DNS mechanisms enlarge the code space, so packet-level decoding is preferable to a single generic Windows status.

What to inspect

Capture the response and decode the base header RCODE plus any extended RCODE carried by EDNS.
Log the responding server, AA and TC flags, queried name/type, and whether TCP fallback occurred.
Use the specific RCODE to choose remediation: record creation does not fix REFUSED, and changing a suffix does not fix FORMERR.
If no parseable response exists, investigate DNS_ERROR_NO_PACKET or DNS_ERROR_BAD_PACKET instead.

References

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