DNS 5 REFUSED vs 18 BADTIME
Both DNS 5 (REFUSED) and 18 (BADTIME) belong to the DNS Response Codes (RCODEs) category. 5 indicates that query refused. The name server refuses to perform the requested operation for policy reasons. Meanwhile, 18 means that signature out of time window. The TSIG signature timestamp is outside the allowed clock skew, indicating a time synchronization issue.
설명
Query refused. The name server refuses to perform the requested operation for policy reasons.
이 코드를 보게 되는 경우
The server rejected your query due to access control — for example, a recursive resolver that only serves its own network, or a zone transfer blocked by ACL.
해결 방법
Check the server's allow-query, allow-recursion, or allow-transfer ACLs. If you are not authorized to use this resolver, switch to a public DNS service.
설명
Signature out of time window. The TSIG signature timestamp is outside the allowed clock skew, indicating a time synchronization issue.
이 코드를 보게 되는 경우
The clocks on the DNS client and server are too far apart (usually more than 5 minutes), causing TSIG signature validation to fail.
해결 방법
Synchronize clocks on both machines using NTP. Check that the TSIG fudge value (allowed skew) is reasonable — the default 300 seconds is usually sufficient.
주요 차이점
DNS 5: Query refused. The name server refuses to perform the requested operation for policy reasons.
DNS 18: Signature out of time window. The TSIG signature timestamp is outside the allowed clock skew, indicating a time synchronization issue.
You encounter 5 when the server rejected your query due to access control — for example, a recursive resolver that only serves its own network, or a zone transfer blocked by ACL.
You encounter 18 when the clocks on the DNS client and server are too far apart (usually more than 5 minutes), causing TSIG signature validation to fail.
언제 어떤 것을 사용할지
For 5 (REFUSED): Check the server's allow-query, allow-recursion, or allow-transfer ACLs. If you are not authorized to use this resolver, switch to a public DNS service. For 18 (BADTIME): Synchronize clocks on both machines using NTP. Check that the TSIG fudge value (allowed skew) is reasonable — the default 300 seconds is usually sufficient.