List of DNS record types
(Redirected from PTR record)
This list of DNS record types is an overview of resource records (RRs) permissible in zone files of the Domain Name System (DNS). It also contains pseudo-RRs.
Resource records
[edit]| Type | Type id (decimal) | Defining RFC | Description | Function |
|---|---|---|---|---|
| A | 1 | RFC 1035[1] | Address record | Returns a 32-bit IPv4 address, most commonly used to map hostnames to an IP address of the host, but it is also used for DNSBLs, storing subnet masks in RFC 1101, etc. |
| AAAA | 28 | RFC 3596[2] | IPv6 address record | Returns a 128-bit IPv6 address, most commonly used to map hostnames to an IP address of the host. |
| AFSDB | 18 | RFC 1183 | AFS database record | Location of database servers of an AFS cell. This record is commonly used by AFS clients to contact AFS cells outside their local domain. A subtype of this record is used by the obsolete DCE/DFS file system. |
| APL | 42 | RFC 3123 | Address Prefix List | Specify lists of address ranges, e.g. in CIDR format, for various address families. Experimental. |
| CAA | 257 | RFC 6844 | Certification Authority Authorization | DNS Certification Authority Authorization, constraining acceptable CAs for a host/domain |
| CDNSKEY | 60 | RFC 7344 | Child copy of DNSKEY record, for transfer to parent | |
| CDS | 59 | RFC 7344 | Child DS | Child copy of DS record, for transfer to parent |
| CERT | 37 | RFC 4398 | Certificate record | Stores PKIX, SPKI, PGP, etc. |
| CNAME | 5 | RFC 1035[1] | Canonical name record | Alias of one name to another: the DNS lookup will continue by retrying the lookup with the new name. |
| CSYNC | 62 | RFC 7477 | Child-to-Parent Synchronization | Specify a synchronization mechanism between a child and a parent DNS zone. Typical example is declaring the same NS records in the parent and the child zone |
| DHCID | 49 | RFC 4701 | DHCP identifier | Used in conjunction with the FQDN option to DHCP |
| DLV | 32769 | RFC 4431 | DNSSEC Lookaside Validation record | For publishing DNSSEC trust anchors outside of the DNS delegation chain. Uses the same format as the DS record. RFC 5074 describes a way of using these records. |
| DNAME | 39 | RFC 6672 | Delegation name record | Alias for a name and all its subnames, unlike CNAME, which is an alias for only the exact name. Like a CNAME record, the DNS lookup will continue by retrying the lookup with the new name. |
| DNSKEY | 48 | RFC 4034 | DNS Key record | The key record used in DNSSEC. Uses the same format as the KEY record. |
| DS | 43 | RFC 4034 | Delegation signer | The record used to identify the DNSSEC signing key of a delegated zone |
| EUI48 | 108 | RFC 7043 | MAC address (EUI-48) | A 48-bit IEEE Extended Unique Identifier. |
| EUI64 | 109 | RFC 7043 | MAC address (EUI-64) | A 64-bit IEEE Extended Unique Identifier. |
| HINFO | 13 | RFC 8482 | Host Information | Providing Minimal-Sized Responses to DNS Queries That Have QTYPE=ANY |
| HIP | 55 | RFC 8005 | Host Identity Protocol | Method of separating the end-point identifier and locator roles of IP addresses. |
| HTTPS | 65 | RFC 9460 | HTTPS Binding | RR that improves performance for clients that need to resolve many resources to access a domain. |
| IPSECKEY | 45 | RFC 4025 | IPsec Key | Key record that can be used with IPsec |
| KEY | 25 | RFC 2535[3] and RFC 2930[4] | Key record | Used only for SIG(0) (RFC 2931) and TKEY (RFC 2930).[5] RFC 3445 eliminated their use for application keys and limited their use to DNSSEC.[6] RFC 3755 designates DNSKEY as the replacement within DNSSEC.[7] RFC 4025 designates IPSECKEY as the replacement for use with IPsec.[8] |
| KX | 36 | RFC 2230 | Key Exchanger record | Used with some cryptographic systems (not including DNSSEC) to identify a key management agent for the associated domain-name. Note that this has nothing to do with DNS Security. It is Informational status, rather than being on the IETF standards-track. It has always had limited deployment, but is still in use. |
| LOC | 29 | RFC 1876 | Location record | Specifies a geographical location associated with a domain name |
| MX | 15 | RFC 1035[1] and RFC 7505 | Mail exchange record | List of mail exchange servers that accept email for a domain |
| NAPTR | 35 | RFC 3403 | Naming Authority Pointer | Allows regular-expression-based rewriting of domain names which can then be used as URIs, further domain names to lookups, etc. |
| NS | 2 | RFC 1035[1] | Name server record | Delegates a DNS zone to use the given authoritative name servers |
| NSEC | 47 | RFC 4034 | Next Secure record | Part of DNSSEC—used to prove a name does not exist. Uses the same format as the (obsolete) NXT record. |
| NSEC3 | 50 | RFC 5155 | Next Secure record version 3 | An extension to DNSSEC that allows proof of nonexistence for a name without permitting zonewalking |
| NSEC3PARAM | 51 | RFC 5155 | NSEC3 parameters | Parameter record for use with NSEC3 |
| OPENPGPKEY | 61 | RFC 7929 | OpenPGP public key record | A DNS-based Authentication of Named Entities (DANE) method for publishing and locating OpenPGP public keys in DNS for a specific email address using an OPENPGPKEY DNS resource record. |
| PTR | 12 | RFC 1035[1] | PTR Resource Record | Pointer to a canonical name. Unlike a CNAME, DNS processing stops and just the name is returned. The most common use is for implementing reverse DNS lookups, but other uses include such things as DNS-SD. |
| RP | 17 | RFC 1183 | Responsible Person | Information about the responsible person(s) for the domain. Usually an email address with the @ replaced by a . |
| RRSIG | 46 | RFC 4034 | DNSSEC signature | Signature for a DNSSEC-secured record set. Uses the same format as the SIG record. |
| SIG | 24 | RFC 2535 | Signature | Signature record used in SIG(0) (RFC 2931) and TKEY (RFC 2930).[7] RFC 3755 designated RRSIG as the replacement for SIG for use within DNSSEC.[7] |
| SMIMEA | 53 | RFC 8162[9] | S/MIME cert association[10] | Associates an S/MIME certificate with a domain name for sender authentication. |
| SOA | 6 | RFC 1035[1] and RFC 2308[11] | Start of [a zone of] authority record | Specifies authoritative information about a DNS zone, including the primary name server, the email of the domain administrator, the domain serial number, and several timers relating to refreshing the zone. |
| SRV | 33 | RFC 2782 | Service locator | Generalized service location record, used for newer protocols instead of creating protocol-specific records such as MX. |
| SSHFP | 44 | RFC 4255 | SSH Public Key Fingerprint | Resource record for publishing SSH public host key fingerprints in the DNS, in order to aid in verifying the authenticity of the host. RFC 6594 defines ECC SSH keys and SHA-256 hashes. See the IANA SSHFP RR parameters registry for details. |
| SVCB | 64 | RFC 9460 | Service Binding | RR that improves performance for clients that need to resolve many resources to access a domain. |
| TA | 32768 | — | DNSSEC Trust Authorities | Part of a deployment proposal for DNSSEC without a signed DNS root. See the IANA database and Weiler Spec for details. Uses the same format as the DS record. |
| TKEY | 249 | RFC 2930 | Transaction Key record | A method of providing keying material to be used with TSIG that is encrypted under the public key in an accompanying KEY RR.[12] |
| TLSA | 52 | RFC 6698 | TLSA certificate association | A record for DANE. RFC 6698 defines "The TLSA DNS resource record is used to associate a TLS server certificate or public key with the domain name where the record is found, thus forming a 'TLSA certificate association'". |
| TSIG | 250 | RFC 2845 | Transaction Signature | Can be used to authenticate dynamic updates as coming from an approved client, or to authenticate responses as coming from an approved recursive name server[13] similar to DNSSEC. |
| TXT | 16 | RFC 1035[1] | Text record | Originally for arbitrary human-readable text in a DNS record. Since the early 1990s, however, this record more often carries machine-readable data, such as specified by RFC 1464, opportunistic encryption, Sender Policy Framework, DKIM, DMARC, DNS-SD, etc. |
| URI | 256 | RFC 7553 | Uniform Resource Identifier | Can be used for publishing mappings from hostnames to URIs. |
| ZONEMD | 63 | RFC 8976 | Message Digests for DNS Zones | Provides a cryptographic message digest over DNS zone data at rest. |
Other types and pseudo-RRs
[edit]Other types of records simply provide some types of information (for example, an HINFO record gives a description of the type of computer/OS a host uses), or others return data used in experimental features. The "type" field is also used in the protocol for various operations.
| Type | Type id. | Defining RFC | Description | Function |
|---|---|---|---|---|
| * | 255 | RFC 1035[1] | All cached records | Returns all records of all types known to the name server. If the name server does not have any information on the name, the request will be forwarded on. The records returned may not be complete. For example, if there is both an A and an MX for a name, but the name server has only the A record cached, only the A record will be returned. Usually referred to as ANY (e.g., in dig, Windows nslookup, and Wireshark). In 2019, RFC8482 [14] standards-track publication led many DNS providers, including Cloudflare,[15] to provide only minimal responses to "ANY" queries, instead of enumerating records. |
| AXFR | 252 | RFC 1035[1] | Authoritative Zone Transfer | Transfer entire zone file from the primary name server to secondary name servers. |
| IXFR | 251 | RFC 1996 | Incremental Zone Transfer | Requests a zone transfer of the given zone but only differences from a previous serial number. This request may be ignored and a full (AXFR) sent in response if the authoritative server is unable to fulfill the request due to configuration or lack of required deltas. |
| OPT | 41 | RFC 6891 | Option | This is a pseudo-record type needed to support EDNS. |
Obsolete record types
[edit]Progress has rendered some of the originally defined record-types obsolete. Of the records listed at IANA, some have limited use, for various reasons. Some are marked obsolete in the list, some are for very obscure services, some are for older versions of services, and some have special notes saying they are "not right".
| Type | Type id. (decimal) |
Defining RFC | Obsoleted by | Description |
|---|---|---|---|---|
| MD | 3 | RFC 883 | RFC 973 | Mail destination (MD) and mail forwarder (MF) records; MAILA is not an actual record type, but a query type which returns MF and/or MD records. RFC 973 replaced these records with the MX record. |
| MF | 4 | |||
| MAILA | 254 | |||
| MB | 7 | RFC 883 | Not formally obsoleted. Unlikely to be ever adopted (RFC 2505). | MB, MG, MR, and MINFO are records to publish subscriber mailing lists. MAILB is a query code which returns one of those records. The intent was for MB and MG to replace the SMTP VRFY and EXPN commands. MR was to replace the "551 User Not Local" SMTP error. Later, RFC 2505 recommended that both VRFY and EXPN be disabled, making MB and MG unnecessary. They were classified as experimental by RFC 1035. |
| MG | 8 | |||
| MR | 9 | |||
| MINFO | 14 | |||
| MAILB | 253 | |||
| WKS | 11 | RFC 883, RFC 1035 | Declared as "not to be relied upon" by RFC 1123 (more in RFC 1127). | Record to describe well-known services supported by a host. Not used in practice. The current recommendation and practice is to determine whether a service is supported on an IP address by trying to connect to it. SMTP is even prohibited from using WKS records in MX processing.[16] |
| NB | 32 | RFC 1002 | Mistakes (from RFC 1002); the numbers are now assigned to NIMLOC and SRV. | |
| NBSTAT | 33 | |||
| NULL | 10 | RFC 883 | RFC 1035 | Obsoleted by RFC 1035. RFC 883 defined "completion queries" (opcode 2 and maybe 3) which used this record. RFC 1035 later reassigned opcode 2 to be "status" and reserved opcode 3. |
| A6 | 38 | RFC 2874 | RFC 6563 | Defined as part of early IPv6 but downgraded to experimental by RFC 3363; later downgraded to historic by RFC 6563. |
| NXT | 30 | RFC 2065 | RFC 3755 | Part of the first version of DNSSEC (RFC 2065). NXT was obsoleted by DNSSEC updates (RFC 3755). At the same time, the domain of applicability for KEY and SIG was also limited to not include DNSSEC use. |
| KEY | 25 | |||
| SIG | 24 | |||
| HINFO | 13 | RFC 883 | Unobsoleted by RFC 8482. Currently used by Cloudflare in response to queries of the type ANY.[17] | Record intended to provide information about host CPU type and operating system. It was intended to allow protocols to optimize processing when communicating with similar peers. |
| RP | 17 | RFC 1183 | RP may be used for certain human-readable information regarding a different contact point for a specific host, subnet, or other domain level label separate than that used in the SOA record. | |
| X25 | 19 | Not in current use by any notable application | ||
| ISDN | 20 | Not in current use by any notable application | ||
| RT | 21 | Not in current use by any notable application | ||
| NSAP | 22 | RFC 1706 | Not in current use by any notable application | |
| NSAP-PTR | 23 | Not in current use by any notable application | ||
| PX | 26 | RFC 2163 | Not in current use by any notable application | |
| EID | 31 | — | Defined by the Nimrod DNS Internet Draft, but never made it to RFC status. Not in current use by any notable application | |
| NIMLOC | 32 | — | ||
| ATMA | 34 | — | Defined by The ATM Forum Committee.[18] | |
| APL | 42 | RFC 3123 | Specify lists of address ranges, e.g. in CIDR format, for various address families. Experimental. | |
| SINK | 40 | — | Defined by the Kitchen Sink Internet Draft, but never made it to RFC status | |
| GPOS | 27 | RFC 1712 | A more limited early version of the LOC record | |
| UINFO | 100 | — | IANA reserved, no RFC documented them [1] and support was removed from BIND in the early 90s. | |
| UID | 101 | — | ||
| GID | 102 | — | ||
| UNSPEC | 103 | — | ||
| SPF | 99 | RFC 4408 | RFC 7208 | Specified as part of the Sender Policy Framework protocol as an alternative to storing SPF data in TXT records, using the same format. It was discontinued in RFC 7208 due to widespread lack of support.[19][20] |
| NINFO | 56 | — | Used to provide status information about a zone. Requested for the IETF draft "The Zone Status (ZS) DNS Resource Record" in 2008. Expired without adoption.[21] | |
| RKEY | 57 | — | Used for encryption of NAPTR records. Requested for the IETF draft "The RKEY DNS Resource Record" in 2008. Expired without adoption.[22] | |
| TALINK | 58 | — | Defined by the DNSSEC Trust Anchor History Service Internet Draft, but never made it to RFC status | |
| NID | 104 | RFC 6742 | Not in use by any notable application and marked as "experimental" | |
| L32 | 105 | |||
| L64 | 106 | |||
| LP | 107 | |||
| DOA | 259 | — | Defined by the DOA over DNS Internet Draft, but never made it to RFC status |
References
[edit]- ^ a b c d e f g h i Paul Mockapetris (November 1987). "RFC 1035: Domain Names - Implementation and Specification". Network Working Group of the IETF (Internet Engineering Task Force). p. 12.
- ^ "RFC 3596: DNS Extensions to Support IP Version 6". The Internet Society. October 2003. Archived from the original on 14 April 2021.
- ^ RFC 2535, §3
- ^ RFC 3445, §1. "The KEY RR was defined in RFC 2930..."
- ^ RFC 2931, §2.4. "SIG(0) on the other hand, uses public key authentication, where the public keys are stored in DNS as KEY RRs and a private key is stored at the signer."
- ^ RFC 3445, §1. "DNSSEC will be the only allowable sub-type for the KEY RR..."
- ^ a b c RFC 3755, §3. "DNSKEY will be the replacement for KEY, with the mnemonic indicating that these keys are not for application use, per RFC3445. RRSIG (Resource Record SIGnature) will replace SIG, and NSEC (Next SECure) will replace NXT. These new types completely replace the old types, except that SIG(0) RFC2931 and TKEY RFC2930 will continue to use SIG and KEY."
- ^ RFC 4025, Abstract. "This record replaces the functionality of the sub-type #4 of the KEY Resource Record, which has been obsoleted by RFC 3445."
- ^ Hoffman, P.; Schlyter, J. (May 2017). "RFC 8162 - Using Secure DNS to Associate Certificates with Domain Names for S/MIME". Internet Engineering Task Force. doi:10.17487/RFC8162. Retrieved 17 October 2018.
- ^ "Domain Name System (DNS) Parameters". Internet Assigned Numbers Authority. September 2018. Retrieved 17 October 2018.
- ^ The minimum field of SOA record is redefined to be the TTL of NXDOMAIN reply in RFC 2308.
- ^ RFC 2930, §6. "... the keying material is sent within the key data field of a TKEY RR encrypted under the public key in an accompanying KEY RR RFC 2535."
- ^ RFC 2845, abstract
- ^
J. Abley, Afilias, O. Gudmundsson, M. Majkowski, Cloudflare Inc., E. Hunt, ISC (January 2019). "RFC 8482: Providing Minimal-Sized Responses to DNS Queries That Have QTYPE=ANY". Ietf Datatracker. Internet Engineering Task Force.
{{cite news}}: CS1 maint: multiple names: authors list (link) - ^ "What happened next: the deprecation of ANY". Cloudflare. 16 March 2019. Retrieved 19 September 2021.
- ^ RFC 1123 sections 2.2, 5.2.12, 6.1.3.6
- ^ "What happened next: the deprecation of ANY". Cloudflare. 13 April 2016. Retrieved 9 March 2019.
- ^ "ATM Name System, V2.0" (PDF). ATM Forum Technical Committee. July 2000. Archived from the original (PDF) on 2019-03-14. Retrieved 14 March 2019.
- ^ Kucherawy, M. (July 2012). "Background on the RRTYPE Issue". Resolution of the Sender Policy Framework (SPF) and Sender ID Experiments. IETF. sec. A. doi:10.17487/RFC6686. RFC 6686. Retrieved August 31, 2013.
- ^ Kitterman, S. (April 2014). "The SPF DNS Record Type". Sender Policy Framework (SPF) for Authorizing Use of Domains in Email, Version 1. IETF. sec. 3.1. doi:10.17487/RFC7208. RFC 7208. Retrieved 26 April 2014.
- ^ Reid, Jim (4 July 2008). "draft-reid-dnsext-zs-01 - The Zone Status (ZS) DNS Resource Record". Ietf Datatracker. IETF. Retrieved 9 March 2019.
- ^ Reid, Jim; Schlyter, Jakob; Timms, Ben (4 July 2008). "draft-reid-dnsext-rkey-00 - The RKEY DNS Resource Record". Ietf Datatracker. IETF. Retrieved 9 March 2019.
Further reading
[edit]- "Domain Name System (DNS) Parameters". Retrieved 2018-08-14.
- "DNS basics - G Suite Administrator Help". Retrieved 2018-11-08.