Domain Name System (DNS) Parameters

Last Updated

  • 2026-08-28

Available Formats

DNS CLASSes

Expert(s)

  • Petr Špaček, Ladislav Lhotka

Reference

  • RFC 6895: Domain Name System (DNS) IANA Considerations
  • RFC 9108: YANG Types for DNS Classes and Resource Record Types

Note

As noted in RFC 6762, Multicast DNS can only carry DNS records with classes in the range 0-32767. Classes in the range 32768 to 65535 are incompatible with Multicast DNS.

Note

When this registry is modified, the YANG module iana-dns-class-rr-type must be updated as defined in RFC 9108.

Available Formats

Decimal Hex Registration Procedures Note
0 0x0000 Standards Action
1-127 0x0000-0x007F IETF Review data CLASSes only
128-253 0x0080-0x00FD IETF Review QCLASSes and meta-CLASSes only
256-32767 0x0100-0x7FFF IETF Review
32768-57343 0x8000-0xDFFF Specification Required data CLASSes only
57344-65279 0xE000-0xFEFF Specification Required QCLASSes and meta-CLASSes only
65280-65534 0xFF00-0xFFFE Private Use
65535 0xFFFF Standards Action
Decimal Hexadecimal Name Reference
0 0x0000 Reserved RFC 6895
1 0x0001 Internet (IN) RFC 1035
2 0x0002 Unassigned
3 0x0003 Chaos (CH) D. Moon, "Chaosnet", A.I. Memo 628, Massachusetts Institute of Technology Artificial Intelligence Laboratory, June 1981.
4 0x0004 Hesiod (HS) Dyer, S., and F. Hsu, "Hesiod", Project Athena Technical Plan - Name Service, April 1987.
5-253 0x0005-0x00FD Unassigned
254 0x00FE QCLASS NONE RFC 2136
255 0x00FF QCLASS * (ANY) RFC 1035
256-65279 0x0100-0xFEFF Unassigned
65280-65534 0xFF00-0xFFFE Reserved for Private Use RFC 6895
65535 0xFFFF Reserved RFC 6895

Resource Record (RR) TYPEs

Expert(s)

  • Roy Arends, Frederico AC Neves, Ólafur Guðmundsson, Ray Bellis

Reference

  • RFC 6895: Domain Name System (DNS) IANA Considerations
  • RFC 1035: Domain names - implementation and specification
  • RFC 9108: YANG Types for DNS Classes and Resource Record Types

Note

When this registry is modified, the YANG module iana-dns-class-rr-type must be updated as defined in RFC 9108.

Available Formats

Decimal Hex Registration Procedures Note
0 0x0000 RRTYPE zero is used as a special indicator for the SIG RR RFC 2931, RFC 4034 and in other circumstances and must never be allocated for ordinary use.
1-127 0x0000-0x007F Expert Review (see mailing list information in RFC 6895) or Standards Action data TYPEs
128-255 0x0080-0x00FF Expert Review (see mailing list information in RFC 6895) or Standards Action Q TYPEs, Meta TYPEs
256-61439 0x0100-0xEFFF Expert Review (see mailing list information in RFC 6895) or Standards Action data RRTYPEs
61440-65279 0xF000-0xFEFF Reserved for future use (IETF Review required to define use)
65280-65534 0xFF00-0xFFFE Private Use
65535 0xFFFF Reserved (Standards Action)
TYPE Value Meaning Reference Template Registration Date
Reserved 0 RFC 6895 2021-03-08
A 1 a host address RFC 1035
NS 2 an authoritative name server RFC 1035
MD 3 a mail destination (OBSOLETE - use MX) RFC 1035
MF 4 a mail forwarder (OBSOLETE - use MX) RFC 1035
CNAME 5 the canonical name for an alias RFC 1035
SOA 6 marks the start of a zone of authority RFC 1035
MB 7 a mailbox domain name (EXPERIMENTAL) RFC 1035
MG 8 a mail group member (EXPERIMENTAL) RFC 1035
MR 9 a mail rename domain name (EXPERIMENTAL) RFC 1035
NULL 10 a null RR (EXPERIMENTAL) RFC 1035
WKS 11 a well known service description RFC 1035
PTR 12 a domain name pointer RFC 1035
HINFO 13 host information RFC 1035
MINFO 14 mailbox or mail list information RFC 1035
MX 15 mail exchange RFC 1035
TXT 16 text strings RFC 1035
RP 17 for Responsible Person RFC 1183
AFSDB 18 for AFS Data Base location RFC 1183; RFC 5864
X25 19 for X.25 PSDN address RFC 1183
ISDN 20 for ISDN address RFC 1183
RT 21 for Route Through RFC 1183
NSAP 22 for NSAP address, NSAP style A record (DEPRECATED) RFC 1706; Moving TPC.INT and NSAP.INT infrastructure domains to historic
NSAP-PTR 23 for domain name pointer, NSAP style (DEPRECATED) RFC 1706; Moving TPC.INT and NSAP.INT infrastructure domains to historic
SIG 24 for security signature RFC 2536; RFC 2931; RFC 3110; RFC 4034
KEY 25 for security key RFC 2536; RFC 2539; RFC 3110; RFC 4034
PX 26 X.400 mail mapping information RFC 2163
GPOS 27 Geographical Position RFC 1712
AAAA 28 IP6 Address RFC 3596
LOC 29 Location Information RFC 1876
NXT 30 Next Domain (OBSOLETE) RFC 2535; RFC 3755
EID 31 Endpoint Identifier Michael Patton; http://ana-3.lcs.mit.edu/~jnc/nimrod/dns.txt 1995-06
NIMLOC 32 Nimrod Locator [1]Michael Patton; http://ana-3.lcs.mit.edu/~jnc/nimrod/dns.txt 1995-06
SRV 33 Server Selection [1]RFC 2782
ATMA 34 ATM Address ATM Forum Technical Committee, "ATM Name System, V2.0", Doc ID: AF-DANS-0152.000, July 2000. Available from and held in escrow by IANA.
NAPTR 35 Naming Authority Pointer RFC 3403
KX 36 Key Exchanger RFC 2230
CERT 37 CERT RFC 4398
A6 38 A6 (OBSOLETE - use AAAA) RFC 2874; RFC 3226; RFC 6563
DNAME 39 DNAME RFC 6672
SINK 40 SINK Donald E. Eastlake, III; draft-eastlake-kitchen-sink-02 1997-11
OPT 41 OPT RFC 3225; RFC 6891
APL 42 APL RFC 3123
DS 43 Delegation Signer RFC 4034
SSHFP 44 SSH Key Fingerprint RFC 4255
IPSECKEY 45 IPSECKEY RFC 4025
RRSIG 46 RRSIG RFC 4034
NSEC 47 NSEC RFC 4034; RFC 9077
DNSKEY 48 DNSKEY RFC 4034
DHCID 49 DHCID RFC 4701
NSEC3 50 NSEC3 RFC 5155; RFC 9077
NSEC3PARAM 51 NSEC3PARAM RFC 5155
TLSA 52 TLSA RFC 6698
SMIMEA 53 S/MIME cert association RFC 8162 SMIMEA/smimea-completed-template 2015-12-01
Unassigned 54
HIP 55 Host Identity Protocol RFC 8005
NINFO 56 NINFO Jim Reid NINFO/ninfo-completed-template 2008-01-21
RKEY 57 RKEY Jim Reid RKEY/rkey-completed-template 2008-01-21
TALINK 58 Trust Anchor LINK Wouter Wijngaards TALINK/talink-completed-template 2010-02-17
CDS 59 Child DS RFC 7344 CDS/cds-completed-template 2011-06-06
CDNSKEY 60 DNSKEY(s) the Child wants reflected in DS RFC 7344 2014-06-16
OPENPGPKEY 61 OpenPGP Key RFC 7929 OPENPGPKEY/openpgpkey-completed-template 2014-08-12
CSYNC 62 Child-To-Parent Synchronization RFC 7477 2015-01-27
ZONEMD 63 Message Digest Over Zone Data RFC 8976 ZONEMD/zonemd-completed-template 2018-12-12
SVCB 64 General-purpose service binding RFC 9460 SVCB/svcb-completed-template 2020-06-30
HTTPS 65 SVCB-compatible type for use with HTTP RFC 9460 HTTPS/https-completed-template 2020-06-30
DSYNC 66 Endpoint discovery for delegation synchronization RFC 9859 DSYNC/dsync-completed-template 2024-12-10
HHIT 67 Hierarchical Host Identity Tag RFC 9886 HHIT/hhit-completed-template 2025-05-20
BRID 68 UAS Broadcast Remote Identification RFC 9886 BRID/brid-completed-template 2025-05-20
UNECE 69 Value coded per a UNECE Recommendation draft-woodcock-faltstrom-external-registry-rrtypes-00 UNECE/unece-completed-template 2026-08-20
ISO 70 Value coded per an ISO standard draft-woodcock-faltstrom-external-registry-rrtypes-00 ISO/iso-completed-template 2026-08-20
Unassigned 71-98
SPF 99 RFC 7208
UINFO 100 IANA-Reserved
UID 101 IANA-Reserved
GID 102 IANA-Reserved
UNSPEC 103 IANA-Reserved
NID 104 RFC 6742 ILNP/nid-completed-template
L32 105 RFC 6742 ILNP/l32-completed-template
L64 106 RFC 6742 ILNP/l64-completed-template
LP 107 RFC 6742 ILNP/lp-completed-template
EUI48 108 an EUI-48 address RFC 7043 EUI48/eui48-completed-template 2013-03-27
EUI64 109 an EUI-64 address RFC 7043 EUI64/eui64-completed-template 2013-03-27
Unassigned 110-127
NXNAME 128 NXDOMAIN indicator for Compact Denial of Existence RFC 9824 NXNAME/nxname-completed-template 2024-07-18
Unassigned 129-248
TKEY 249 Transaction Key RFC 2930
TSIG 250 Transaction Signature RFC 8945
IXFR 251 incremental transfer RFC 1995
AXFR 252 transfer of an entire zone RFC 1035; RFC 5936
MAILB 253 mailbox-related RRs (MB, MG or MR) RFC 1035
MAILA 254 mail agent RRs (OBSOLETE - see MX) RFC 1035
* 255 A request for some or all records the server has available RFC 1035; RFC 6895; RFC 8482
URI 256 URI RFC 7553 URI/uri-completed-template 2011-02-22
CAA 257 Certification Authority Restriction RFC 8659 CAA/caa-completed-template 2011-04-07
AVC 258 Application Visibility and Control Wolfgang Riedel AVC/avc-completed-template 2016-02-26
DOA 259 Digital Object Architecture draft-durand-doa-over-dns-02 DOA/doa-completed-template 2017-08-30
AMTRELAY 260 Automatic Multicast Tunneling Relay RFC 8777 AMTRELAY/amtrelay-completed-template 2019-02-06
RESINFO 261 Resolver Information as Key/Value Pairs RFC 9606 RESINFO/resinfo-completed-template 2023-11-02
WALLET 262 Public wallet address Paul Hoffman WALLET/wallet-completed-template 2024-06-21
CLA 263 BP Convergence Layer Adapter draft-johnson-dns-ipn-cla-07 CLA/cla-completed-template 2024-07-25
IPN 264 BP Node Number draft-johnson-dns-ipn-cla-07 IPN/ipn-completed-template 2024-07-25
Unassigned 265-32767
TA 32768 DNSSEC Trust Authorities Sam Weiler; Deploying DNSSEC Without a Signed Root. Technical Report 1999-19, Information Networking Institute, Carnegie Mellon University, April 2004. 2005-12-13
DLV 32769 DNSSEC Lookaside Validation (OBSOLETE) RFC 8749; RFC 4431
Unassigned 32770-65279
Private use 65280-65534
Reserved 65535

DNS OpCodes

Registration Procedure(s)

  • Standards Action

Reference

  • RFC 6895: Domain Name System (DNS) IANA Considerations
  • RFC 1035: Domain names - implementation and specification

Available Formats

OpCode Name Reference
0 Query RFC 1035
1 IQuery (Inverse Query, OBSOLETE) RFC 3425
2 Status RFC 1035
3 Unassigned
4 Notify RFC 1996
5 Update RFC 2136
6 DNS Stateful Operations (DSO) RFC 8490
7-15 Unassigned

DNS RCODEs

Reference

  • RFC 6895: Domain Name System (DNS) IANA Considerations
  • RFC 1035: Domain names - implementation and specification

Available Formats

Range Registration Procedures
0-3840 IETF Review
3841-4095 Private Use
4096-65534 IETF Review
65535 Reserved (Standards Action)
RCODE Name Description Reference
0 NoError No Error RFC 1035
1 FormErr Format Error RFC 1035
2 ServFail Server Failure RFC 1035
3 NXDomain Non-Existent Domain RFC 1035
4 NotImp Not Implemented RFC 1035
5 Refused Query Refused RFC 1035
6 YXDomain Name Exists when it should not RFC 2136; RFC 6672
7 YXRRSet RR Set Exists when it should not RFC 2136
8 NXRRSet RR Set that should exist does not RFC 2136
9 NotAuth Server Not Authoritative for zone RFC 2136
9 NotAuth Not Authorized RFC 8945
10 NotZone Name not contained in zone RFC 2136
11 DSOTYPENI DSO-TYPE Not Implemented RFC 8490
12-15 Unassigned
16 BADVERS Bad OPT Version RFC 6891
16 BADSIG TSIG Signature Failure RFC 8945
17 BADKEY Key not recognized RFC 8945
18 BADTIME Signature out of time window RFC 8945
19 BADMODE Bad TKEY Mode RFC 2930
20 BADNAME Duplicate key name RFC 2930
21 BADALG Algorithm not supported RFC 2930
22 BADTRUNC Bad Truncation RFC 8945
23 BADCOOKIE Bad/missing Server Cookie RFC 7873
24-3840 Unassigned
3841-4095 Reserved for Private Use RFC 6895
4096-65534 Unassigned
65535 Reserved, can be allocated by Standards Action RFC 6895

AFSDB RR Subtype

Registration Procedure(s)

Reference

  • RFC 6895: Domain Name System (DNS) IANA Considerations
  • RFC 1035: Domain names - implementation and specification

Available Formats

Decimal Hexadecimal Description Reference
0 0x0000 Reserved; registry closed RFC 6895
1 0x0001 Andrews File Service v3.0 Location Service RFC 1183
2 0x0002 DCE/NCA root cell directory node RFC 1183
3-65279 0x0003-0xFEFF Not allocated; registry closed
65280-65534 0xFF00-0xFFFE Reserved for Private Use RFC 6895
65535 0xFFFF Reserved; registry closed RFC 6895

DHCID RR Identifier Type Codes

Registration Procedure(s)

  • Standards Action

Expert(s)

  • Ólafur Guðmundsson

Reference

  • RFC 4701: A DNS Resource Record (RR) for Encoding Dynamic Host Configuration Protocol (DHCP) Information (DHCID RR)

Note

Registration rules to be as follows:

New DHCID RR type codes are tentatively assigned after the specification for the associated type code, published as an Internet Draft, has received expert review by a designated expert. The final assignment of DHCID RR type codes is through Standards Action, as defined in RFC 2434.

Available Formats

Identifier Type Code Identifier Reference
0x0000 The 1-octet 'htype' followed by 'hlen' octets of 'chaddr' from a DHCPv4 client's DHCPREQUEST. RFC 4701
0x0001 The data octets (i.e., the Type and Client-Identifier fields) from a DHCPv4 client's Client Identifier option. RFC 4701
0x0002 The client's DUID (i.e., the data octets of a DHCPv6 client's Client Identifier option or the DUID field from a DHCPv4 client's Client Identifier option). RFC 4701
0x0003-0xFFFE Unassigned RFC 4701
0xFFFF Reserved RFC 4701

DHCID RR Digest Type Codes

Registration Procedure(s)

  • Standards Action

Reference

  • RFC 4701: A DNS Resource Record (RR) for Encoding Dynamic Host Configuration Protocol (DHCP) Information (DHCID RR)

Available Formats

Digest Type Code Description Reference
0 Reserved RFC 4701
1 SHA-256 RFC 4701
2-255 Unassigned

DNS Label Types

Registration Procedure(s)

  • Standards Action

Reference

  • RFC 6891: Extension Mechanisms for DNS (EDNS(0))

Note

The top 2 bits of the first byte of an DNS label indicate the type of label.

Available Formats

Value Type Status Reference
0 0 Normal label lower 6 bits is the length of the label Standard RFC 1035
1 1 Compressed label the lower 6 bits and the 8 bits from next octet form a pointer to the compression target. Standard RFC 1035
0 1 Extended label type the lower 6 bits of this type (section 3) indicate the type of label in use Proposed RFC 6891
0 1 0 0 0 0 0 1 Binary Label Historic RFC 3364; RFC 3363; RFC 2673; RFC 6891
0 1 1 1 1 1 1 1 Reserved for future expansion. Proposed RFC 6891
1 0 Unallocated

DNS EDNS0 Option Codes (OPT)

Expert(s)

  • Ólafur Guðmundsson (primary), Frederico AC Neves (secondary), Ray Bellis (secondary), Roy Arends (secondary)

Reference

Note

Registrations made by standards-track documents are listed as "Standard," and by non-standards-track documents as "Optional." Registrations for which there are no final specifications are listed as "On-Hold."

Available Formats

Range Registration Procedures
1-65000 Expert Review
65001-65534 Local/Experimental Use
Value Name Status Reference
0 Reserved RFC 6891
1 LLQ Optional RFC 8764
2 Update Lease Standard RFC 9664
3 NSID Standard RFC 5001
4 Reserved draft-cheshire-edns0-owner-option-00
5 DAU Standard RFC 6975
6 DHU Standard RFC 6975
7 N3U Standard RFC 6975
8 edns-client-subnet Optional RFC 7871
9 EDNS EXPIRE Optional RFC 7314
10 COOKIE Standard RFC 7873
11 edns-tcp-keepalive Standard RFC 7828
12 Padding Standard RFC 7830
13 CHAIN Standard RFC 7901
14 edns-key-tag Optional RFC 8145
15 Extended DNS Error Standard RFC 8914
16 EDNS-Client-Tag Optional draft-bellis-dnsop-edns-tags-01
17 EDNS-Server-Tag Optional draft-bellis-dnsop-edns-tags-01
18 Report-Channel Standard RFC 9567
19 ZONEVERSION Standard RFC 9660
20 MQTYPE-Query Optional RFC 10029
21 MQTYPE-Response Optional RFC 10029
22 EDE-EXTRA-TEXT-LANGUAGE Optional draft-muks-dns-filtering-05
23 FILTERING-CONTACT Optional draft-muks-dns-filtering-05
24 FILTERING-ORGANIZATION Optional draft-muks-dns-filtering-05
25 FILTERING-DB Optional draft-muks-dns-filtering-05
26 Structured DNS Error Standard RFC-ietf-dnsop-structured-dns-error-27
27-20291 Unassigned
20292 Umbrella Ident Optional https://developer.cisco.com/docs/cloud-security/#!integrating-network-devices/rdata-description; Cisco CIE DNS team
20293-26945 Unassigned
26946 DeviceID Optional https://developer.cisco.com/docs/cloud-security/#!network-devices-getting-started/response-codes; Cisco CIE DNS team
26947-65000 Unassigned
65001-65534 Reserved for Local/Experimental Use RFC 6891
65535 Reserved for future expansion RFC 6891

DNS Header Flags

Registration Procedure(s)

  • Standards Action

Reference

  • RFC 6895: Domain Name System (DNS) IANA Considerations
  • RFC 1035: Domain names - implementation and specification

Note

In DNS query header there is a flag field in the second 16 bit word in query from bit 5 through bit 11 (RFC 1035, Section 4.1.1)

Available Formats

Bit Flag Description Reference
bit 5 AA Authoritative Answer RFC 1035
bit 6 TC Truncated Response RFC 1035
bit 7 RD Recursion Desired RFC 1035
bit 8 RA Recursion Available RFC 1035
bit 9 Reserved
bit 10 AD Authentic Data RFC 4035; RFC 6840; RFC Errata 4924
bit 11 CD Checking Disabled RFC 4035; RFC 6840; RFC Errata 4927

EDNS Header Flags (16 bits)

Registration Procedure(s)

  • Standards Action

Reference

  • RFC 6891: Extension Mechanisms for DNS (EDNS(0))

Available Formats

Bit Flag Description Reference
Bit 0 DO DNSSEC answer OK RFC 4035; RFC 3225; RFC 6840; RFC Errata 4928
Bit 1 CO Compact Answers OK RFC 9824
Bit 2 DE Delegation Extensions (TEMPORARY - registered 2026-07-20, expires 2027-07-20) draft-ietf-dnsop-delext-08
Bit 3-15 Reserved

EDNS version Number (8 bits)

Registration Procedure(s)

  • Standards Action

Reference

  • RFC 6891: Extension Mechanisms for DNS (EDNS(0))

Available Formats

Range Description Reference
0 EDNS version 0 RFC 6891
1-255 Unassigned

Child Synchronization (CSYNC) Flags

Registration Procedure(s)

  • Standards Action

Reference

  • RFC 7477: Child-to-Parent Synchronization in DNS

Available Formats

Bit Flag Description Reference
0 immediate Immediately process this CSYNC record. RFC 7477, Section 3
1 soaminimum Require a SOA serial number greater than the one specified. RFC 7477, Section 2.1.1.1
2-15 Unassigned

Underscored and Globally Scoped DNS Node Names

Registration Procedure(s)

  • Expert Review

Expert(s)

  • Frederico A C Neves, Paul Wouters

Reference

  • RFC 8552: Scoped Interpretation of DNS Resource Records through "Underscored" Naming of Attribute Leaves

Available Formats

RR Type _NODE NAME Reference
* _example RFC 8552, Section 4.1.4
CDNSKEY _signal RFC 9615
CDS _signal RFC 9615
DSYNC _dsync RFC 9859
HTTPS _https RFC 9460
NULL _ta-* [2] RFC 8145
OPENPGPKEY _openpgpkey RFC 7929
SMIMEA _smimecert RFC 8162
SRV _dccp RFC 2782
SRV _http RFC 4386
SRV _ipv6 RFC 5026
SRV _ldap RFC 4386
SRV _ocsp RFC 4386
SRV _sctp RFC 2782
SRV _sip RFC 5509
SRV _stun RFC 8489, Section 8.1
SRV _stuns RFC 8489, Section 8.1
SRV _tcp RFC 2782
SRV _turn RFC 8656, Section 4.1
SRV _turns RFC 8656, Section 4.1
SRV _udp RFC 2782
SRV _xmpp RFC 3921
SVCB _dns RFC 9461
TLSA _dane RFC 7671
TLSA _sctp RFC 6698
TLSA _tcp RFC 6698
TLSA _udp RFC 6698
TXT _x402 draft-hawkins-x402-dns-discovery-01
TXT _acme-challenge RFC 8555
TXT _dmarc RFC 9989
TXT _domainkey RFC 6376
TXT _er RFC 9567
TXT _for-sale RFC 10023
TXT _mta-sts RFC 8461
TXT _nnu-verification https://nnu.us/specifications/nnu-domain-verification-1.0.txt
TXT _spf RFC 7208
TXT _splitdns-challenge RFC 9704
TXT _sztp RFC 8572
TXT _tcp RFC 6763
TXT _tls RFC 8460
TXT _udp RFC 6763
TXT _validation-contactemail https://cabforum.org/wp-content/uploads/CA-Browser-Forum-BR-1.7.4.pdf
TXT _validation-contactphone https://cabforum.org/wp-content/uploads/CA-Browser-Forum-BR-1.7.4.pdf
TXT _vouch RFC 5518
URI _acct RFC 7566; RFC Errata 7064
URI _dccp RFC 4340; RFC Errata 7066
URI _email RFC 6118
URI _ems RFC 6118
URI _fax RFC 6118
URI _ft RFC 6118
URI _h323 RFC 6118
URI _iax RFC 6315; RFC Errata 7065
URI _ical-access RFC 6118
URI _ical-sched RFC 6118
URI _ifax RFC 6118
URI _im RFC 6118
URI _mms RFC 6118
URI _pres RFC 6118
URI _pstn RFC 6118
URI _sctp RFC 4340; RFC Errata 7067
URI _sip RFC 6118
URI _sms RFC 6118
URI _tcp RFC 4340; RFC Errata 7068
URI _udp RFC 4340; RFC Errata 7068
URI _unifmsg RFC 6118
URI _vcard RFC 6118
URI _videomsg RFC 6118
URI _voice RFC 6118
URI _voicemsg RFC 6118
URI _vpim RFC 6118
URI _web RFC 6118
URI _xmpp RFC 6118

DSO Type Codes

Expert(s)

  • Ted Lemon, Sara Dickinson, John Dickinson

Reference

Available Formats

Range Registration Procedures
0x0004-0x003F Standards Action
0x0040-0xF7FF Expert Review
0xF800-0xFBFF Experimental/Local Use
0xFC00-0xFFFF Standards Action
Type Name Early Data Status Reference
0x0000 Reserved NO Standards Track RFC 8490
0x0001 KeepAlive OK Standards Track RFC 8490
0x0002 RetryDelay NO Standards Track RFC 8490
0x0003 EncryptionPadding NA Standards Track RFC 8490
0x0004-0x003F Unassigned, reserved for DSO session-management TLVs NO
0x0040 SUBSCRIBE OK Standards Track RFC 8765, Section 6.2
0x0041 PUSH NO Standards Track RFC 8765, Section 6.3
0x0042 UNSUBSCRIBE NO Standards Track RFC 8765, Section 6.4
0x0043 RECONFIRM NO Standards Track RFC 8765, Section 6.5
0x0044-0xF7FF Unassigned NO
0xF800-0xFBFF Reserved for Experimental/Local Use NO RFC 8490
0xFC00-0xFFFF Reserved for future expansion NO

Extended DNS Error Codes

Reference

Available Formats

Range Registration Procedures
0-49151 First Come First Served
49152-65535 Private Use
INFO-CODE Purpose Reference
0 Other Error RFC 8914, Section 4.1
1 Unsupported DNSKEY Algorithm RFC 8914, Section 4.2
2 Unsupported DS Digest Type RFC 8914, Section 4.3
3 Stale Answer RFC 8914, Section 4.4; RFC 8767
4 Forged Answer RFC 8914, Section 4.5
5 DNSSEC Indeterminate RFC 8914, Section 4.6
6 DNSSEC Bogus RFC 8914, Section 4.7
7 Signature Expired RFC 8914, Section 4.8
8 Signature Not Yet Valid RFC 8914, Section 4.9
9 DNSKEY Missing RFC 8914, Section 4.10
10 RRSIGs Missing RFC 8914, Section 4.11
11 No Zone Key Bit Set RFC 8914, Section 4.12
12 NSEC Missing RFC 8914, Section 4.13
13 Cached Error RFC 8914, Section 4.14
14 Not Ready RFC 8914, Section 4.15
15 Blocked RFC 8914, Section 4.16
16 Censored RFC 8914, Section 4.17
17 Filtered RFC 8914, Section 4.18
18 Prohibited RFC 8914, Section 4.19
19 Stale NXDomain Answer RFC 8914, Section 4.20
20 Not Authoritative RFC 8914, Section 4.21
21 Not Supported RFC 8914, Section 4.22
22 No Reachable Authority RFC 8914, Section 4.23
23 Network Error RFC 8914, Section 4.24
24 Invalid Data RFC 8914, Section 4.25
25 Signature Expired before Valid https://github.com/NLnetLabs/unbound/pull/604#discussion_r802678343; Willem Toorop
26 Too Early RFC 9250
27 Unsupported NSEC3 Iterations Value RFC 9276
28 Unable to conform to policy draft-homburg-dnsop-codcp-00
29 Synthesized https://github.com/PowerDNS/pdns/pull/12334; Otto Moerbeek
30 Invalid Query Type RFC 9824
31 Rate Limited draft-muks-dns-ede-rate-limited-02, Section 2
32 Over Quota draft-muks-dns-ede-rate-limited-02, Section 3
33 Negative Trust Anchor draft-farrokhi-dnsop-ede-nta-00
34 New Delegation Only draft-ietf-deleg-10
35 Blocked by Upstream DNS Server RFC-ietf-dnsop-structured-dns-error-27
36-49151 Unassigned
49152-65535 Reserved for Private Use RFC 8914, Section 5.2

EXTRA-TEXT JSON Names

Registration Procedure(s)

  • IETF Review

Reference

Available Formats

JSON Name Field Meaning Description Reference
c contact The contact details of the IT/InfoSec team to report misclassified DNS filtering RFC-ietf-dnsop-structured-dns-error-27, Section 4
j justification UTF-8-encoded RFC 5198 textual justification for a particular DNS filtering RFC-ietf-dnsop-structured-dns-error-27, Section 4
s sub-error Integer representing the sub-error code for this DNS filtering case RFC-ietf-dnsop-structured-dns-error-27, Section 4
o organization UTF-8-encoded human-friendly name of the organization that filtered this particular DNS query RFC-ietf-dnsop-structured-dns-error-27, Section 4
l language Indicates the language of the "j" and "o" fields as defined in RFC 5646 RFC-ietf-dnsop-structured-dns-error-27, Section 4

Contact URI Schemes

Registration Procedure(s)

  • IETF Review

Reference

Available Formats

Name Meaning Reference
tel Telephone Number RFC 3966
mailto Internet mail RFC 6068

Extended DNS Sub-Error Codes

Registration Procedure(s)

  • IETF Review

Reference

Available Formats

Number Meaning EDE Codes Applicability Reference
0 Reserved Not used RFC-ietf-dnsop-structured-dns-error-27, Section 6.1
1 Malware "Blocked", "Blocked by Upstream DNS Server", "Filtered" RFC 5901, Section 5.5
2 Phishing "Blocked", "Blocked by Upstream DNS Server", "Filtered" RFC 5901, Section 5.5
3 Spam "Blocked", "Blocked by Upstream DNS Server", "Filtered" RFC 4949
4 Spyware "Blocked", "Blocked by Upstream DNS Server", "Filtered" RFC 4949
5 Network operator policy "Blocked" RFC-ietf-dnsop-structured-dns-error-27, Section 6.2
6 DNS operator policy "Blocked" RFC-ietf-dnsop-structured-dns-error-27, Section 6.3
7-255 Unassigned

ZONEMD Schemes

Expert(s)

  • Warren Kumari, Duane Wessels, Wes Hardaker

Reference

Available Formats

Range Registration Procedures
1-239 Specification Required
240-254 Private Use
Value Description Mnemonic Reference
0 Reserved RFC 8976
1 Simple ZONEMD collation SIMPLE RFC 8976
2-239 Unassigned
240-254 Reserved for Private Use N/A RFC 8976
255 Reserved RFC 8976

ZONEMD Hash Algorithms

Expert(s)

  • Warren Kumari, Duane Wessels, Wes Hardaker

Reference

Available Formats

Range Registration Procedures
1-239 Specification Required
240-254 Private Use
Value Description Mnemonic Reference
0 Reserved RFC 8976
1 SHA-384 SHA384 RFC 8976
2 SHA-512 SHA512 RFC 8976
3-239 Unassigned
240-254 Reserved for Private Use N/A RFC 8976
255 Reserved RFC 8976

DNS-over-QUIC Error Codes

Expert(s)

  • Sara Dickinson, Christian Huitema

Reference

  • RFC 9250: DNS over Dedicated QUIC Connections

Available Formats

Range Registration Procedures
provisional (greater than 0x3f) Expert Review
provisional registration Date field update First Come First Served
permanent, 0x00-0x3f Standards Action or IESG Approval
permanent, greater than 0x3f Specification Required
Value Error Description Status Specification Date Contact
0x0 DOQ_NO_ERROR No error permanent RFC 9250, Section 4.3 2022-04-01 DPRIVE working group
0x1 DOQ_INTERNAL_ERROR Implementation error permanent RFC 9250, Section 4.3 2022-04-01 DPRIVE working group
0x2 DOQ_PROTOCOL_ERROR Generic protocol violation permanent RFC 9250, Section 4.3 2022-04-01 DPRIVE working group
0x3 DOQ_REQUEST_CANCELLED Request cancelled by client permanent RFC 9250, Section 4.3 2022-04-01 DPRIVE working group
0x4 DOQ_EXCESSIVE_LOAD Closing a connection for excessive load permanent RFC 9250, Section 4.3 2022-04-01 DPRIVE working group
0x5 DOQ_UNSPECIFIED_ERROR No error reason specified permanent RFC 9250, Section 4.3 2022-04-01 DPRIVE working group
0xd098ea5e DOQ_ERROR_RESERVED Alternative error code used for tests permanent RFC 9250, Section 4.3 2022-04-01 DPRIVE working group

DNS Catalog Zones Properties

Expert(s)

  • Peter Thomassen, Ondřej Surý, Willem Toorop

Reference

Note

This registry applies to Catalog Zones schema version "2" as specified in RFC 9432.

Available Formats

Range Registration Procedures
property prefix ends in the label "ext" Private Use
all other property prefixes Expert Review
Property Prefix Description Status Reference
zones List of member zones Standards Track RFC 9432
version Schema version Standards Track RFC 9432
coo Change of Ownership Standards Track RFC 9432
group Group Standards Track RFC 9432
*.ext Custom properties Private Use RFC 9432

DNS Resolver Information Keys

Registration Procedure(s)

  • Specification Required

Expert(s)

  • Tirumal Reddy, Mohamed Boucadair, Ben Schwartz

Reference

Available Formats

Name Description Reference
qnamemin The presence of the key name indicates that QNAME minimisation is enabled. RFC 9606
exterr Lists the set of enabled extended DNS errors. It must be an INFO-CODE decimal value in the Extended DNS Error Codes registry. RFC 9606
infourl Provides a URL that points to unstructured resolver information that is used for troubleshooting. RFC 9606
deleg The presence of the key indicates that the DELEG protocol is supported. (TEMPORARY - registered 2026-08-24, expires 2027-08-24) draft-ietf-deleg-11

ZONEVERSION TYPE Values

Expert(s)

  • Hugo Salgado, Mauricio Vergara Ereche, Duane Wessels

Reference

  • RFC 9660: The DNS Zone Version (ZONEVERSION) Option

Available Formats

Range Registration Procedures
0-245 Specification Required
246-254 Private Use
255 Reserved
ZONEVERSION TYPE Mnemonic Reference
0 SOA-SERIAL RFC 9660
1-245 Unassigned
246-254 Reserved for Private Use RFC 9660
255 Reserved RFC 9660

DSYNC: Location of Synchronization Endpoints

Registration Procedure(s)

  • Expert Review

Expert(s)

  • Johan Stenstam, Peter Thomassen, John Levine

Reference

Available Formats

RRtype Scheme (Mnemonic) Purpose Reference
0 Null scheme (no-op) RFC 9859
CDS 1 (NOTIFY) Delegation management RFC 9859
CSYNC 1 (NOTIFY) Delegation management RFC 9859
2-127 Unassigned
128-255 Reserved for Private Use RFC 9859

Contact Information

Name Contact URI Last Updated
Cisco CIE DNS team cie-eng.dns-team&cisco.com 2021-08-31
Donald E. Eastlake, III d3e3e3&gmail.com 1997-11
DPRIVE working group dns-privacy&ietf.org 2022-04-01
Jim Reid jim&telnic.org 2008-01-21
Michael Patton map&bbn.com 1995-06
Otto Moerbeek otto.moerbeek&powerdns.com 2023-03-29
Paul Hoffman paul.hoffman&icann.org 2024-07-01
Sam Weiler weiler+iana&tislabs.com 2005-12
Willem Toorop willem&nlnetlabs.nl 2022-02-11
Wolfgang Riedel wolfgang&cisco.com 2016-02-26
Wouter Wijngaards wouter&nlnetlabs.nl 2010-02-17

Footnotes

[1]

In RFC 1002, two types are defined. It is not clear that these are in use, though if so their assignment does conflict with those above.

NB      32      NetBIOS general Name Service
NBSTAT  33      NetBIOS NODE STATUS
[2]

From RFC 8552, Section 4.1.3:

Under the NULL RR, the entry "_ta-*" denotes all node names beginning with the string "_ta-*". It does NOT refer to a DNS wildcard specification.