DNS 1 FORMERR vs 7 YXRRSET
Both DNS 1 (FORMERR) and 7 (YXRRSET) belong to the DNS Response Codes (RCODEs) category. 1 indicates that format error. The name server was unable to interpret the query due to a malformed DNS message. Meanwhile, 7 means that rR Set Exists when it should not. A resource record set exists that the update prerequisite says should not.
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.
Description
RR Set Exists when it should not. A resource record set exists that the update prerequisite says should not.
When You See It
A DNS UPDATE failed because a specific RRset (e.g., an A record) already exists when the prerequisite required it to be absent.
How to Fix
Delete the conflicting RRset before retrying the update, or adjust your prerequisite conditions to match the actual zone state.
Key Differences
DNS 1: Format error. The name server was unable to interpret the query due to a malformed DNS message.
DNS 7: RR Set Exists when it should not. A resource record set exists that the update prerequisite says should not.
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.
You encounter 7 when a DNS UPDATE failed because a specific RRset (e.g., an A record) already exists when the prerequisite required it to be absent.
When to Use Which
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. For 7 (YXRRSET): Delete the conflicting RRset before retrying the update, or adjust your prerequisite conditions to match the actual zone state.