2026-03-05 Petr Špaček, Ladislav Lhotka As noted in , 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. When this registry is modified, the YANG module iana-dns-class-rr-type must be updated as defined in . 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 0 0x0000 Reserved 1 0x0001 Internet (IN) 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 255 0x00FF QCLASS * (ANY) 256-65279 0x0100-0xFEFF Unassigned 65280-65534 0xFF00-0xFFFE Reserved for Private Use 65535 0xFFFF Reserved Roy Arends, Frederico AC Neves, Ólafur Guðmundsson, Ray Bellis When this registry is modified, the YANG module iana-dns-class-rr-type must be updated as defined in . 0 0x0000 RRTYPE zero is used as a special indicator for the SIG RR , and in other circumstances and must never be allocated for ordinary use. 1-127 0x0000-0x007F Expert Review (see mailing list information in ) or Standards Action data TYPEs 128-255 0x0080-0x00FF Expert Review (see mailing list information in ) or Standards Action Q TYPEs, Meta TYPEs 256-61439 0x0100-0xEFFF Expert Review (see mailing list information in ) 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) Reserved 0 A 1 a host address NS 2 an authoritative name server MD 3 a mail destination (OBSOLETE - use MX) MF 4 a mail forwarder (OBSOLETE - use MX) CNAME 5 the canonical name for an alias SOA 6 marks the start of a zone of authority MB 7 a mailbox domain name (EXPERIMENTAL) MG 8 a mail group member (EXPERIMENTAL) MR 9 a mail rename domain name (EXPERIMENTAL) NULL 10 a null RR (EXPERIMENTAL) WKS 11 a well known service description PTR 12 a domain name pointer HINFO 13 host information MINFO 14 mailbox or mail list information MX 15 mail exchange TXT 16 text strings RP 17 for Responsible Person AFSDB 18 for AFS Data Base location X25 19 for X.25 PSDN address ISDN 20 for ISDN address RT 21 for Route Through NSAP 22 for NSAP address, NSAP style A record (DEPRECATED) Moving TPC.INT and NSAP.INT infrastructure domains to historic NSAP-PTR 23 for domain name pointer, NSAP style (DEPRECATED) Moving TPC.INT and NSAP.INT infrastructure domains to historic SIG 24 for security signature KEY 25 for security key PX 26 X.400 mail mapping information GPOS 27 Geographical Position AAAA 28 IP6 Address LOC 29 Location Information NXT 30 Next Domain (OBSOLETE) EID 31 Endpoint Identifier NIMLOC 32 Nimrod Locator SRV 33 Server Selection 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 KX 36 Key Exchanger CERT 37 CERT A6 38 A6 (OBSOLETE - use AAAA) DNAME 39 DNAME SINK 40 SINK OPT 41 OPT APL 42 APL DS 43 Delegation Signer SSHFP 44 SSH Key Fingerprint IPSECKEY 45 IPSECKEY RRSIG 46 RRSIG NSEC 47 NSEC DNSKEY 48 DNSKEY DHCID 49 DHCID NSEC3 50 NSEC3 NSEC3PARAM 51 NSEC3PARAM TLSA 52 TLSA SMIMEA 53 S/MIME cert association SMIMEA/smimea-completed-template Unassigned 54 HIP 55 Host Identity Protocol NINFO 56 NINFO NINFO/ninfo-completed-template RKEY 57 RKEY RKEY/rkey-completed-template TALINK 58 Trust Anchor LINK TALINK/talink-completed-template CDS 59 Child DS CDS/cds-completed-template CDNSKEY 60 DNSKEY(s) the Child wants reflected in DS OPENPGPKEY 61 OpenPGP Key OPENPGPKEY/openpgpkey-completed-template CSYNC 62 Child-To-Parent Synchronization ZONEMD 63 Message Digest Over Zone Data ZONEMD/zonemd-completed-template SVCB 64 General-purpose service binding SVCB/svcb-completed-template HTTPS 65 SVCB-compatible type for use with HTTP HTTPS/https-completed-template DSYNC 66 Endpoint discovery for delegation synchronization DSYNC/dsync-completed-template HHIT 67 Hierarchical Host Identity Tag HHIT/hhit-completed-template BRID 68 UAS Broadcast Remote Identification BRID/brid-completed-template Unassigned 69-98 SPF 99 UINFO 100 IANA-Reserved UID 101 IANA-Reserved GID 102 IANA-Reserved UNSPEC 103 IANA-Reserved NID 104 ILNP/nid-completed-template L32 105 ILNP/l32-completed-template L64 106 ILNP/l64-completed-template LP 107 ILNP/lp-completed-template EUI48 108 an EUI-48 address EUI48/eui48-completed-template EUI64 109 an EUI-64 address EUI64/eui64-completed-template Unassigned 110-127 NXNAME 128 NXDOMAIN indicator for Compact Denial of Existence NXNAME/nxname-completed-template Unassigned 129-248 TKEY 249 Transaction Key TSIG 250 Transaction Signature IXFR 251 incremental transfer AXFR 252 transfer of an entire zone MAILB 253 mailbox-related RRs (MB, MG or MR) MAILA 254 mail agent RRs (OBSOLETE - see MX) * 255 A request for some or all records the server has available URI 256 URI URI/uri-completed-template CAA 257 Certification Authority Restriction CAA/caa-completed-template AVC 258 Application Visibility and Control AVC/avc-completed-template DOA 259 Digital Object Architecture DOA/doa-completed-template AMTRELAY 260 Automatic Multicast Tunneling Relay AMTRELAY/amtrelay-completed-template RESINFO 261 Resolver Information as Key/Value Pairs RESINFO/resinfo-completed-template WALLET 262 Public wallet address WALLET/wallet-completed-template CLA 263 BP Convergence Layer Adapter CLA/cla-completed-template IPN 264 BP Node Number IPN/ipn-completed-template Unassigned 265-32767 TA 32768 DNSSEC Trust Authorities Deploying DNSSEC Without a Signed Root. Technical Report 1999-19, Information Networking Institute, Carnegie Mellon University, April 2004. DLV 32769 DNSSEC Lookaside Validation (OBSOLETE) Unassigned 32770-65279 Private use 65280-65534 Reserved 65535 In , 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 Standards Action 0 Query 1 IQuery (Inverse Query, OBSOLETE) 2 Status 3 Unassigned 4 Notify 5 Update 6 DNS Stateful Operations (DSO) 7-15 Unassigned 0-3840 IETF Review 3841-4095 Private Use 4096-65534 IETF Review 65535 Reserved (Standards Action) 0 NoError No Error 1 FormErr Format Error 2 ServFail Server Failure 3 NXDomain Non-Existent Domain 4 NotImp Not Implemented 5 Refused Query Refused 6 YXDomain Name Exists when it should not 7 YXRRSet RR Set Exists when it should not 8 NXRRSet RR Set that should exist does not 9 NotAuth Server Not Authoritative for zone 9 NotAuth Not Authorized 10 NotZone Name not contained in zone 11 DSOTYPENI DSO-TYPE Not Implemented 12-15 Unassigned 16 BADVERS Bad OPT Version 16 BADSIG TSIG Signature Failure 17 BADKEY Key not recognized 18 BADTIME Signature out of time window 19 BADMODE Bad TKEY Mode 20 BADNAME Duplicate key name 21 BADALG Algorithm not supported 22 BADTRUNC Bad Truncation 23 BADCOOKIE Bad/missing Server Cookie 24-3840 Unassigned 3841-4095 Reserved for Private Use 4096-65534 Unassigned 65535 Reserved, can be allocated by Standards Action Registry closed per 0 0x0000 Reserved; registry closed 1 0x0001 Andrews File Service v3.0 Location Service 2 0x0002 DCE/NCA root cell directory node 3-65279 0x0003-0xFEFF Not allocated; registry closed 65280-65534 0xFF00-0xFFFE Reserved for Private Use 65535 0xFFFF Reserved; registry closed Standards Action Ólafur Guðmundsson 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 . 0x0000 The 1-octet 'htype' followed by 'hlen' octets of 'chaddr' from a DHCPv4 client's DHCPREQUEST. 0x0001 The data octets (i.e., the Type and Client-Identifier fields) from a DHCPv4 client's Client Identifier option. 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). 0x0003-0xFFFE Unassigned 0xFFFF Reserved Standards Action 0 Reserved 1 SHA-256 2-255 Unassigned Standards Action The top 2 bits of the first byte of an DNS label indicate the type of label. 0 0 Normal label lower 6 bits is the length of the label Standard 1 1 Compressed label the lower 6 bits and the 8 bits from next octet form a pointer to the compression target. Standard 0 1 Extended label type the lower 6 bits of this type (section 3) indicate the type of label in use Proposed 0 1 0 0 0 0 0 1 Binary Label Historic 0 1 1 1 1 1 1 1 Reserved for future expansion. Proposed 1 0 Unallocated 1-65000 Expert Review 65001-65534 Local/Experimental Use Ólafur Guðmundsson (primary), Frederico AC Neves (secondary), Ray Bellis (secondary), Roy Arends (secondary) 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." 0 Reserved 1 LLQ Optional 2 Update Lease Standard 3 NSID Standard 4 Reserved 5 DAU Standard 6 DHU Standard 7 N3U Standard 8 edns-client-subnet Optional 9 EDNS EXPIRE Optional 10 COOKIE Standard 11 edns-tcp-keepalive Standard 12 Padding Standard 13 CHAIN Standard 14 edns-key-tag Optional 15 Extended DNS Error Standard 16 EDNS-Client-Tag Optional 17 EDNS-Server-Tag Optional 18 Report-Channel Standard 19 ZONEVERSION Standard 20 MQTYPE-Query Optional 21 MQTYPE-Response Optional 22-20291 Unassigned 20292 Umbrella Ident Optional 20293-26945 Unassigned 26946 DeviceID Optional 26947-65000 Unassigned 65001-65534 Reserved for Local/Experimental Use 65535 Reserved for future expansion Standards Action In DNS query header there is a flag field in the second 16 bit word in query from bit 5 through bit 11 ( section 4.1.1) bit 5 AA Authoritative Answer bit 6 TC Truncated Response bit 7 RD Recursion Desired bit 8 RA Recursion Available bit 9 Reserved bit 10 AD Authentic Data bit 11 CD Checking Disabled Standards Action Bit 0 DO DNSSEC answer OK Bit 1 CO Compact Answers OK Bit 2-15 Reserved Standards Action 0 EDNS version 0 1-255 Unassigned Standards Action 0 immediate Immediately process this CSYNC record. RFC7477, Section 3 1 soaminimum Require a SOA serial number greater than the one specified. RFC7477, Section 2.1.1.1 2-15 Unassigned Expert Review Frederico A C Neves, Paul Wouters * _example RFC8552, Section 4.1.4 CDNSKEY _signal CDS _signal DSYNC _dsync HTTPS _https NULL _ta-* OPENPGPKEY _openpgpkey SMIMEA _smimecert SRV _dccp SRV _http SRV _ipv6 SRV _ldap SRV _ocsp SRV _sctp SRV _sip SRV _stun RFC8489, Section 8.1 SRV _stuns RFC8489, Section 8.1 SRV _tcp SRV _turn RFC8656, Section 4.1 SRV _turns RFC8656, Section 4.1 SRV _udp SRV _xmpp SVCB _dns TLSA _dane TLSA _sctp TLSA _tcp TLSA _udp TXT _acme-challenge TXT _dmarc TXT _domainkey TXT _er TXT _for-sale TXT _mta-sts TXT _spf TXT _splitdns-challenge TXT _sztp TXT _tcp TXT _udp TXT _validation-contactemail TXT _validation-contactphone TXT _vouch URI _acct URI _dccp URI _email URI _ems URI _fax URI _ft URI _h323 URI _iax URI _ical-access URI _ical-sched URI _ifax URI _im URI _mms URI _pres URI _pstn URI _sctp URI _sip URI _sms URI _tcp URI _udp URI _unifmsg URI _vcard URI _videomsg URI _voice URI _voicemsg URI _vpim URI _web URI _xmpp From RFC8552, Section 4.1.3 _ta: 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. 0x0004-0x003F Standards Action 0x0040-0xF7FF Expert Review 0xF800-0xFBFF Experimental/Local Use 0xFC00-0xFFFF Standards Action Ted Lemon, Sara Dickinson, John Dickinson 0x0000 Reserved NO Standards Track 0x0001 KeepAlive OK Standards Track 0x0002 RetryDelay NO Standards Track 0x0003 EncryptionPadding NA Standards Track 0x0004-0x003F Unassigned, reserved for DSO session-management TLVs NO 0x0040 SUBSCRIBE OK Standards Track RF8765, Section 6.2 0x0041 PUSH NO Standards Track RF8765, Section 6.3 0x0042 UNSUBSCRIBE NO Standards Track RF8765, Section 6.4 0x0043 RECONFIRM NO Standards Track RF8765, Section 6.5 0x0044-0xF7FF Unassigned NO 0xF800-0xFBFF Reserved for Experimental/Local Use NO 0xFC00-0xFFFF Reserved for future expansion NO 0-49151 First Come First Served 49152-65535 Private Use 0 Other Error RFC8914, Section 4.1 1 Unsupported DNSKEY Algorithm RFC8914, Section 4.2 2 Unsupported DS Digest Type RFC8914, Section 4.3 3 Stale Answer RFC8914, Section 4.4 4 Forged Answer RFC8914, Section 4.5 5 DNSSEC Indeterminate RFC8914, Section 4.6 6 DNSSEC Bogus RFC8914, Section 4.7 7 Signature Expired RFC8914, Section 4.8 8 Signature Not Yet Valid RFC8914, Section 4.9 9 DNSKEY Missing RFC8914, Section 4.10 10 RRSIGs Missing RFC8914, Section 4.11 11 No Zone Key Bit Set RFC8914, Section 4.12 12 NSEC Missing RFC8914, Section 4.13 13 Cached Error RFC8914, Section 4.14 14 Not Ready RFC8914, Section 4.15 15 Blocked RFC8914, Section 4.16 16 Censored RFC8914, Section 4.17 17 Filtered RFC8914, Section 4.18 18 Prohibited RFC8914, Section 4.19 19 Stale NXDomain Answer RFC8914, Section 4.20 20 Not Authoritative RFC8914, Section 4.21 21 Not Supported RFC8914, Section 4.22 22 No Reachable Authority RFC8914, Section 4.23 23 Network Error RFC8914, Section 4.24 24 Invalid Data RFC8914, Section 4.25 25 Signature Expired before Valid 26 Too Early 27 Unsupported NSEC3 Iterations Value 28 Unable to conform to policy 29 Synthesized 30 Invalid Query Type 31 Rate Limited draft-muks-dns-ede-rate-limited-02, Section 2 32 Over Quota draft-muks-dns-ede-rate-limited-02, Section 3 33-49151 Unassigned 49152-65535 Reserved for Private Use RFC8914, Section 5.2 1-239 Specification Required 240-254 Private Use Warren Kumari, Duane Wessels, Wes Hardaker 0 Reserved 1 Simple ZONEMD collation SIMPLE 2-239 Unassigned 240-254 Reserved for Private Use N/A 255 Reserved 1-239 Specification Required 240-254 Private Use Warren Kumari, Duane Wessels, Wes Hardaker 0 Reserved 1 SHA-384 SHA384 2 SHA-512 SHA512 3-239 Unassigned 240-254 Reserved for Private Use N/A 255 Reserved Ondřej Surý, Donald Eastlake A Server Cookie method (construction and pseudorandom algorithm) is determined by the Version in the first byte of the Cookie and by the Cookie size. Server Cookie size is limited to the inclusive range of 8 to 32 bytes. Version 1-239, Size 8-32 Expert Review Version 240-254, Size 8-32 Private Use 0 8-32 Reserved 1 8-15 Unassigned 1 16 SipHash-2-4 1 17-32 Unassigned 2-239 8-32 Unassigned 240-254 8-32 Reserved for Private Use 255 8-32 Reserved 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 Sara Dickinson, Christian Huitema 0x0 DOQ_NO_ERROR No error permanent RFC9250, Section 4.3 2022-04-01 0x1 DOQ_INTERNAL_ERROR Implementation error permanent RFC9250, Section 4.3 2022-04-01 0x2 DOQ_PROTOCOL_ERROR Generic protocol violation permanent RFC9250, Section 4.3 2022-04-01 0x3 DOQ_REQUEST_CANCELLED Request cancelled by client permanent RFC9250, Section 4.3 2022-04-01 0x4 DOQ_EXCESSIVE_LOAD Closing a connection for excessive load permanent RFC9250, Section 4.3 2022-04-01 0x5 DOQ_UNSPECIFIED_ERROR No error reason specified permanent RFC9250, Section 4.3 2022-04-01 0xd098ea5e DOQ_ERROR_RESERVED Alternative error code used for tests permanent RFC9250, Section 4.3 2022-04-01 property prefix ends in the label "ext" Private Use all other property prefixes Expert Review Peter Thomassen, Ondřej Surý, Willem Toorop This registry applies to Catalog Zones schema version "2" as specified in . zones List of member zones Standards Track version Schema version Standards Track coo Change of Ownership Standards Track group Group Standards Track *.ext Custom properties Private Use Tirumal Reddy, Mohamed Boucadair, Ben Schwartz Specification Required qnamemin The presence of the key name indicates that QNAME minimisation is enabled. exterr Lists the set of enabled extended DNS errors. It must be an INFO-CODE decimal value in the Extended DNS Error Codes registry. infourl Provides a URL that points to unstructured resolver information that is used for troubleshooting. 0-245 Specification Required 246-254 Private Use 255 Reserved Hugo Salgado, Mauricio Vergara Ereche, Duane Wessels 0 SOA-SERIAL 1-245 Unassigned 246-254 Reserved for Private Use 255 Reserved Expert Review Johan Stenstam, Peter Thomassen, John Levine 0 Null scheme (no-op) CDS 1 (NOTIFY) Delegation management CSYNC 1 (NOTIFY) Delegation management 2-127 Unassigned 128-255 Reserved for Private Use Cisco CIE DNS team mailto:cie-eng.dns-team&cisco.com 2021-08-31 Donald E. Eastlake, III mailto:d3e3e3&gmail.com 1997-11 DPRIVE working group mailto:dns-privacy&ietf.org 2022-04-01 Jim Reid mailto:jim&telnic.org 2008-01-21 Michael Patton mailto:map&bbn.com 1995-06 Otto Moerbeek mailto:otto.moerbeek&powerdns.com 2023-03-29 Paul Hoffman mailto:paul.hoffman&icann.org 2024-07-01 Sam Weiler mailto:weiler+iana&tislabs.com 2005-12 Willem Toorop mailto:willem&nlnetlabs.nl 2022-02-11 Wolfgang Riedel mailto:wolfgang&cisco.com 2016-02-26 Wouter Wijngaards mailto:wouter&nlnetlabs.nl 2010-02-17