RCODE	Name	Description	Reference
0	NoError	No Error	RFC1035
1	FormErr	Format Error	RFC1035
2	ServFail	Server Failure	RFC1035
3	NXDomain	Non-Existent Domain	RFC1035
4	NotImp	Not Implemented	RFC1035
5	Refused	Query Refused	RFC1035
6	YXDomain	Name Exists when it should not	RFC2136, RFC6672
7	YXRRSet	RR Set exists when it should not	RFC2136
8	NXRRSet	RR Set that should exist does not	RFC2136
9	NotAuth	Server Not Authoritative for zone	RFC2136
9	NotAuth	Not Authorized	RFC8945
10	NotZone	Name not contained in zone	RFC2136
11	DSOTYPENI	DSO-TYPE Not Implemented	RFC8940
12-15	Unassigned
16	BADVERS	Bad OPT Version	RFC6891
16	BADSIG	TSIG Signature Failure	RFC8945
17	BADKEY	Key not recognised	RFC8945
18	BADTIME	Signature out of time window	RFC8945
19	BADMODE	Bad TKEY Mode	RFC2930
20	BADNAME	Duplicate key name	RFC2930
21	BADALG	Algorithm not supported	RFC2930
22	BADTRUNC	Bad Truncation	RFC8945
23	BADCOOKIE	Bad/missing Server Cookie	RFC7873
24-3840	Unassigned
3841-4095	Reserved for Private Use		RFC6895
4096-65534	Unassigned
65535	Reserved, can be allocated by Standards Action		RFC6895