Skip to main content This browser is no longer supported. Show
Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. Resource Records
In this articleA resource record, commonly referred to as an RR, is the unit of information entry in DNS zone files; RRs are the basic building blocks of host-name and IP information and are used to resolve all DNS queries. Resource records exist as many types to provide extended name-resolution services. Different types of RRs have different formats, as they contain different data. In general, however, many RRs share a common format, as the following address resource records example illustrates. The following fictional example explains the fields found in an A resource record:
The following resource record types are commonly used in DNS:
There are many other resource record types in DNS. For more information, see DNS WMI Provider Reference. Additional resourcesAdditional resourcesIn this articleIntroduction DNS records or zone files store information about domains. They consist of a series of text files written in the DNS syntax and are stored on DNS servers. In this tutorial, we take you through a comprehensive alphabetical list of DNS record types, explaining how they work, and provide examples and use cases. A (address) records are one of the most basic and commonly used DNS record types. They translate domain names and store them as IP addresses. A records can only hold IPv4 addresses. An example of an A record is:
In the example above, the record is made up of the following elements:
AAAA RecordAAAA records work the same as A records in that they store IP addresses connected to domain names. The only difference is that AAAA records hold IPv6 addresses. AFSDB RecordAFSDB records connect a domain name to an AFS (Andrew File System) number. This record type is commonly used to contact AFS cells outside the client's local domain. An AFSDB record example is:
The example above contains the following elements:
ATMA RecordAn ATMA record maps a domain name to an ATM (Asynchronous Transfer Mode) address, expressed in either E.164 (decimal) or NSAP (hexadecimal) format. ATMA record entries use the following elements:
In the example above:
CAA RecordCAA records allow domain owners to determine which certificate authorities can issue certificates to that domain and all its subdomains. If there is no CAA record, anyone can issue certificates to the domain.
The CAA record example above contains the following elements:
CERT RecordCERT records provide a space for storing certificates and related certificate revocation lists (CRL). The certificates can verify the authenticity of sending and receiving parties, while CRLs identify unauthorized parties. CERT records contain the following data fields:
CNAME RecordA CNAME (canonical name) record is used instead of an A record if a domain is an alias for another domain. Because of this, all CNAME records point to a domain instead of an IP address. For example, in a domain called alias-domain.com which works as an alias for real-domain.com, a CNAME record for would look like this:
This record contains:
CNAME records usually contain subdomains that point to a domain's A or AAAA record. This prevents having to create an extra A or AAAA record for each subdomain. It is not recommended to have CNAME records pointing to other CNAME records, as this creates unnecessary steps to the DNS lookup process. DHCID RecordDHCID records store DHCP (Dynamic Host Configuration Protocol) information. DHCP servers and clients generally create them through dynamic updates. DNAME RecordDNAME records are used to create an alias for every subdomain of a domain. They are similar to CNAME records, with the main difference being that CNAME can only store a single alias domain without any subdomains. DNSKEY RecordDNSKEY records hold public data keys used to verify DNSSEC signatures. An example of a DNSKEY record might look like:
In the example above:
DS RecordDS (delegation signer) records are used to secure delegations in DNSSEC. These records reference DNSKEY records in their sub-delegated zones. DS records contain the following elements:
HINFO RecordHINFO (host information) records store details about the hardware and operating system the host is using. Due to security concerns, only certain application protocols use this information which is rarely stored on public servers. A typical HINFO record contains:
ISDN RecordAn ISDN record maps the domain name to an ISDN (Integrated Services Digital Network) telephone number, using the ITU-T E.163/E.164 international telephone numbering standards. This record type can contain an optional hexadecimal number as an ISDN sub-address. MB, MG, MINFO, MR RecordsMB, MG, MINFO, and MR records work as an alternative to the more commonly used MX records:
MX RecordMX (mail exchange) records store instructions for directing emails to mail servers following the SMTP protocol. An MX record might look like:
In this example:
Note: An MX record can only point to a name of an email server. This means that each referenced email server must also have a valid A record specifying its IP address. NAPTR RecordAn NS (nameserver) record indicates which server contains the DNS records for a given domain. Domains usually have several NS records pointing to primary and backup nameservers for that domain. A nameserver is a type of DNS server that contains all DNS records for a single domain.
The example above contains the following elements:
NSAP RecordNSAP records map domain names to NSAP addresses, expressed in hexadecimal digits. NSAP addresses are similar to IP addresses and are used to identify equipment connected to an ATM network. NSEC RecordAn NSEC (next secure) record links to the next record in the DNSSEC sorting order and lists the record types that exist for that record's name. These records are commonly used as a part of DNSSEC validation to verify if a record name exists or not. NSEC records contain the following elements:
NSEC3 RecordNSEC3 (next secure version 3) records work the same as NSEC records, except NSEC3 uses cryptographically hashed record names to prevent record names in a zone from being enumerated. These records contain the following elements:
NSEC3PARAM RecordAn NSEC3PARAM (NSEC3 parameters) record contains a list of parameters associated with an NSEC3 record. It determines which NSEC3 records to include as a response when DNSSEC requests a nonexistent record name or type. NSEC3PARAM records include the Hash algorithm, Flags, Iterations, and Salt elements of an appropriate NSEC3 record. PTR RecordPTR (pointer) records serve as an inverse of A or AAAA records. They map IP addresses to domain names and help perform reverse DNS lookups. PTR records store IP addresses in reverse:
RP RecordRP (responsible person) records store mailboxes of persons responsible for a given domain name. Additional information, such as the responsible person's phone number or address, can be provided in a TXT record that the RP record maps to. An example of an RP record:
In this example:
RRSIG RecordAn RRSIG record holds a DNSSEC signature for a set of one or more DNS records with the same name and type. These signatures can be verified with the public keys stored in DNSKEY records. RRSIG records have the following elements:
RT RecordRT (route through) records are used to specify intermediate hosts that provide routing to the domain name stored in the record. Multiple intermediates can route to the same domain, with the lower preference value deciding who tries first. Each intermediate host must also have a valid A record present. SOA RecordThe SOA (start of authority) record holds important information about a domain or zone. These records are required by IETF standards and are an important element of zone transfers. SOA records detail the following zone properties:
SRV RecordSRV (service) records store host and port information for internet services, such as email or VoIP. Some internet protocols need valid SRV records to function. SRV records hold the following information:
TLSA RecordTLSA (Transport Layer Security Authentication) records store keys used in a domain's TLS servers. The names of TLSA records are made up of a port number, protocol name, and TLS server host name. These records detail certificate usage, selector, and matching type as numeric values with a range of 0-255 and certificate association data as a hexadecimal value. TXT RecordTXT (text) records are used to store descriptive text. They are often used in combination with other record types to provide additional information that doesn't fit the format of other records.
The example above shows a typical TXT record. It contains the following elements:
Note: Text strings in TXT records have a maximum length of 255 characters. X25 RecordX25 records map domain names to a PSDN (Public Switched Data Network) address number following the X.121 international numbering plan. Conclusion After reading this article, you should have a basic understanding of the various DNS record types. You can use the guide as a reference and reminder when you need quick information on a record type. What is the resource record DNS uses for IPv4 hostname to an IP address?The A Record points your hostname to an IP address.
This is one of the most frequently used records in the DNS Zones and it is an essential part of your DNS configuration. The record A specifies IP address (IPv4) for given host.
Which record maps an IPv4 address to a hostname?Address Mapping record (A Record)—also known as a DNS host record, stores a hostname and its corresponding IPv4 address. IP Version 6 Address record (AAAA Record)—stores a hostname and its corresponding IPv6 address.
What are AAAA records used for?Like A records, AAAA records enable client devices to learn the IP address for a domain name. The client device can then connect with and load the website. AAAA records are only used when a domain has an IPv6 address in addition to an IPv4 address, and when the client device in question is configured to use IPv6.
Which DNS resource records maps a domain name to an IPv4 address?1. A record. The A record is the most important DNS record type. The "A" in A record stands for "address." An A record shows the IP address for a specific hostname or domain.
|