DNS NXDOMAIN (RCODE 3) vs NOERROR (RCODE 0)
DNS NXDOMAIN and NOERROR are the two most common DNS responses, representing opposite outcomes. NXDOMAIN means the queried domain name does not exist at all, while NOERROR means the domain exists even if the specific record type was not found (empty answer with NOERROR).
Mô tả
Non-Existent Domain. The queried domain name does not exist in the DNS namespace.
Khi bạn thấy mã này
The domain has no DNS records at all — either it was never registered, has expired, or you have a typo in the hostname.
Cách khắc phục
Double-check the domain spelling. If you own the domain, verify your registrar settings and ensure the nameservers are correctly delegated.
Mô tả
No error condition. The query completed successfully and the response contains the requested data.
Khi bạn thấy mã này
This is the normal, successful response to any DNS query — the name was resolved and the answer section contains the requested records.
Cách khắc phục
No fix needed. RCODE 0 means the DNS lookup succeeded as expected.
Sự khác biệt chính
NXDOMAIN means the domain name itself does not exist — no records of any type exist for this name.
NOERROR means the name exists — the query succeeded, though the answer section may be empty if the specific record type is absent.
NOERROR with an empty answer means the domain exists but has no records of the requested type (e.g., no AAAA record).
NXDOMAIN is cached per the SOA negative TTL; NOERROR responses are cached per the record's TTL.
NXDOMAIN triggers 'DNS_PROBE_FINISHED_NXDOMAIN' in browsers; NOERROR with empty answer may trigger a different code path.
Khi nào dùng cái nào
NXDOMAIN is generated by authoritative nameservers when a queried name has no records of any type. NOERROR is the standard success response. When debugging DNS issues, remember that NOERROR with an empty answer is different from NXDOMAIN — the domain exists, but the specific record type (A, AAAA, MX, etc.) is not configured. Use `dig example.com ANY` to check what records exist.