DNS 4 NOTIMP vs 5 REFUSED
Both DNS 4 (NOTIMP) and 5 (REFUSED) belong to the DNS Response Codes (RCODEs) category. 4 indicates that not Implemented. The name server does not support the requested query type or operation. Meanwhile, 5 means that query refused. The name server refuses to perform the requested operation for policy reasons.
説明
Not Implemented. The name server does not support the requested query type or operation.
このコードが表示される場合
You sent a query type (e.g., IXFR, dynamic update) that the server does not support or has disabled.
解決方法
Verify the server supports the query type you are using. If you need zone transfers or dynamic updates, enable them in the server configuration.
説明
Query refused. The name server refuses to perform the requested operation for policy reasons.
このコードが表示される場合
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.
解決方法
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.
主な違い
DNS 4: Not Implemented. The name server does not support the requested query type or operation.
DNS 5: Query refused. The name server refuses to perform the requested operation for policy reasons.
You encounter 4 when you sent a query type (e.g., IXFR, dynamic update) that the server does not support or has disabled.
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.
どちらをいつ使うか
For 4 (NOTIMP): Verify the server supports the query type you are using. If you need zone transfers or dynamic updates, enable them in the server configuration. 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.