DNS 0 NOERROR vs 1 FORMERR
Both DNS 0 (NOERROR) and 1 (FORMERR) belong to the DNS Response Codes (RCODEs) category. 0 indicates that no error condition. The query completed successfully and the response contains the requested data. Meanwhile, 1 means that format error. The name server was unable to interpret the query due to a malformed DNS message.
Description
No error condition. The query completed successfully and the response contains the requested data.
When You See It
This is the normal, successful response to any DNS query — the name was resolved and the answer section contains the requested records.
How to Fix
No fix needed. RCODE 0 means the DNS lookup succeeded as expected.
Description
Format error. The name server was unable to interpret the query due to a malformed DNS message.
When You See It
Your DNS client or library sent a query the server could not parse, often caused by a buggy resolver, corrupted packet, or unsupported EDNS options.
How to Fix
Check your DNS client or library version for known bugs. Capture the raw query with dig or Wireshark and verify it conforms to the DNS wire format.
Key Differences
DNS 0: No error condition. The query completed successfully and the response contains the requested data.
DNS 1: Format error. The name server was unable to interpret the query due to a malformed DNS message.
You encounter 0 when this is the normal, successful response to any DNS query — the name was resolved and the answer section contains the requested records.
You encounter 1 when your DNS client or library sent a query the server could not parse, often caused by a buggy resolver, corrupted packet, or unsupported EDNS options.
When to Use Which
For 0 (NOERROR): No fix needed. RCODE 0 means the DNS lookup succeeded as expected. For 1 (FORMERR): Check your DNS client or library version for known bugs. Capture the raw query with dig or Wireshark and verify it conforms to the DNS wire format.