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.
描述
Not Implemented. The name server does not support the requested query type or operation.
何时出现
You sent a query type (e.g., IXFR, dynamic update) that the server does not support or has disabled.
如何修复
Verify the server supports the query type you are using. If you need zone transfers or dynamic updates, enable them in the server configuration.
描述
Query refused. The name server refuses to perform the requested operation for policy reasons.
何时出现
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.
如何修复
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.
主要区别
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.
何时使用哪个
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.