Description: Host address (A) resource record. Maps a DNS domain name to an Internet Protocol (IP) version 4 32-bit address. For more information, see RFC 1035.

owner class  ttl  A  


host1.example.microsoft.com.     IN  A


Description: IPv6 host address (AAAA) resource record. Maps a DNS domain name to an Internet Protocol (IP) version 6 128-bit address. For more information, see RFC 1886.

owner  class  ttl  AAAA  


ipv6_host1.example.microsoft.com.     IN  AAAA  4321:0:1:2:3:4:567:89ab


Description: Andrew File System Database (AFSDB) resource record. Maps a DNS domain name in the server_host_name field to the host name for a server computer of a server subtype. The subtype field can have either of the following recognized and supported values:

  • A value of 1 to indicate that the server is an AFS version 3.0 volume location server for the named AFS cell.

  • A value of 2 to indicate that the server is an authenticated name server holding the cell-root directory node for the server that uses either Open Software Foundation's (OSF) DCE authenticated cell-naming system or HP/Apollo's Network Computing Architecture (NCA).

For more information, see RFC 1183.

owner  ttl  class  AFSDB  
subtype  server_host_name


example.microsoft.com.   AFSDB   1 afs-server1.example.microsoft.com.


Description: Asynchronous Transfer Mode address (ATMA) resource record. Maps a DNS domain name in the owner field to an ATM address referenced in the atm_address field.

For more information, see "ATM Name System Specification Version 1.0" at the ATM Forum FTP site. At the ATM Forum FTP site, download af-saa-0069.000.doc or af-saa-0069.000.rtf.


  • Web addresses can change, so you might be unable to connect to the Web site or sites mentioned here.

owner  ttl  class  ATMA  


atm-host   ATMA   47.0079.00010200000000000000.00a03e000002.00


Description: Canonical name (CNAME) resource record. Maps an aliased or alternate DNS domain name in the owner field to a canonical or primary DNS domain name specified in the canonical_name field. The canonical or primary DNS domain name used in the data is required and must resolve to a valid DNS domain name in the namespace.

owner  ttl  class  CNAME  


aliasname.example.microsoft.com.   CNAME   truename.example.microsoft.com.


Description: Host information (HINFO) resource record. Specifies the type of CPU and operating system in the cpu_type and os_type fields, respectively, for the host DNS domain name in the owner field. Well-known CPU and operating system types that are most often used are noted in RFC 1700. This information can be used by application protocols such as FTP, which use special procedures when communicating with computers of a known CPU and operating system type.

owner  ttl  class  HINFO  
cpu_type  os_type


my-computer-name.example.microsoft.com.    HINFO   INTEL-386  WIN32


Description: Integrated Services Digital Network (ISDN) resource record. Maps a DNS domain name to an ISDN telephone number. Telephone numbers used with this record should follow ITU-T E.163/E.164 international telephone numbering standards, which are compatible with current international phone numbering plans already in use. For more information, see RFC 1183.

owner  ttl  class  ISDN  
isdn_address  sub_address


my-isdn-host.example.microsoft.com.    ISDN   141555555539699 002


Description: Public key resource record. Contains a public key that is associated with a zone. In full DNSSEC implementation, resolvers and servers use KEY resource records to authenticate SIG resource records received from a signed zones. KEY resource records are signed by the parent zone, allowing a server that knows a parent zone's public key to discover and verify the child zone's key. Name servers or resolvers receiving resource records from a signed zone obtain the corresponding SIG record then retrieve the zone's KEY record. For more information, see RFC 2535.

owner  class  KEY  protocol  digital_signature_algorithm (DSA)  public_key


widgets.microsoft.com IN KEY 0x0000 3 0


Description: Mailbox (MB) resource record. Maps a specified domain mailbox name in the owner field to a mailbox host name in mailbox_hostname. The mailbox host name must be the same as a valid host address (A) resource record already used by a host in the same zone. Additionally, the specified host must have a domain mailbox that accepts mail for the specified owner. For more information, see RFC 1035.

owner  ttl  class  MB  


mailbox.example.microsoft.com.    MB   mailhost1.example.microsoft.com


Description: Mail group (MG) resource record. Used to add domain mailboxes, each specified by a mailbox (MB) resource record in the current zone, to the domain mailing group identified by owner in this resource record. Names used in the mailbox_name field must be identical to valid mailbox (MB) resource records already present in the current zone. For more information, see RFC 1035.

owner  ttl  class  MG  


administrator.example.microsoft.com.    MG   mailbox1.example.microsoft.com


Description: Mailbox mail list information (MINFO) resource record. Specifies (in responsible_mailbox) a domain mailbox name for a responsible person who maintains a mailing list or mailbox specified in the owner field. The error_mailbox field can also be used to specify a domain mailbox that receives error messages related to this mailing list or mailbox. Mailboxes specified for responsible contacts and error forwarding must be the same as valid mailbox (MB) records that already exist in the current zone. For more information, see RFC 1035.

owner  ttl  class  MINFO  
responsible_mailbox  error_mailbox


administrator.example.microsoft.com.    MINFO  resp-mbox.example.microsoft.com err-mbox.example.microsoft.com


Description: Mailbox renamed (MR) resource record. Specifies a domain mailbox name in new_renamed_mailbox, the proper rename of an existing mailbox specified in the owner field. An MR resource record is often used as a forwarding entry for a user who has moved to a different mailbox. MR records do not cause additional section processing. For more information, see RFC 1035.

owner  ttl  class  MR  


old-mbox.example.microsoft.com.    MR  new-renamed-mbox.example.microsoft.com 


Description: Mail exchanger (MX) resource record. Provides message routing to a mail exchanger host, as specified in mail_exchanger_host, for mail sent to the domain name specified in the owner field. A 2-digit preference value indicates preferred ordering if multiple exchanger hosts are specified. Each exchanger host must have a corresponding host (A) address resource record in a valid zone. For more information, see RFC 1035.

Syntax: owner  ttl  class  MX  preference  mail_exchanger_host


example.microsoft.com.    MX  10 mailserver1.example.microsoft.com 


Description: Used to map a DNS domain name as specified in owner to the name of hosts operating DNS servers specified in the name_server_domain_name field.

Syntax:  owner  ttl  IN  NS  name_server_domain_name


example.microsoft.com.    IN NS  nameserver1.example.microsoft.com


Description: Next resource record. NXT resource records indicate the nonexistence of a name in a zone by creating a chain of all of the literal owner names in that zone. They also indicate what resource record types are present for an existing name. For more information, see RFC 2535.

owner  class  NXT  next_domain_name
  last_record_type  NXT


east.widgets.microsoft.com. IN NXT ftp.widgets.microsoft.com. A NXT


Description: Option resource record. One OPT resource record can be added to the additional data section of either a DNS request or response. An OPT resource record belongs to a particular transport level message, such as UDP, and not to actual DNS data. Only one OPT resource record is allowed, but not required, per message. For more information, see RFC 2671.

name  OPT  class  ttl  
rdlen  rdata


null  OPT  IN  1280  0  0


Description: Pointer (PTR) resource record. Points from the name in owner to another location in the DNS namespace as specified by targeted_domain_name. Often used in special domains such as the in-addr.arpa domain tree to provide reverse lookups of address-to-name mappings. In most cases, each record provides information that points to another DNS domain name location, such as a corresponding host (A) address resource record in a forward lookup zone. For more information, see RFC 1035.

owner  ttl  class  PTR  

Example:    PTR  host.example.microsoft.com.


Description: Responsible Person (RP) resource record. Specifies the domain mailbox name for a responsible person in mailbox_name. This name is then mapped to a domain name in text_record_name for which (TXT) resource records exist in the same zone. When RP records are used in DNS queries, subsequent queries are used to retrieve associated text (TXT) resource record information. For more information, see RFC 1183.

owner  ttl  class  RP  mailbox_name  


example.microsoft.com.               RP    admin.example.microsoft.com.  admin-info.example.microsoft.com.
admin-info.example.microsoft.com.    TXT  "Joe Administrator, (555) 555-0110" 


Description: Route through (RT) resource record. Provides an intermediate host binding for internal hosts that do not have a direct wide area network (WAN) or external network connection. The RT record is similar to the MX record in that any communication from an internal host is routed through the intermediate_host for the destination DNS domain name specified in the owner field. A 2-digit preference value is used to set priority if multiple intermediate routing hosts are specified. For each intermediate host specified, a corresponding host (A) address resource record is needed in the current zone. For more information, see RFC 1183.

owner  ttl  class  RT  
preference  intermediate_host


example.microsoft.com.    RT    2 lan-router.example.microsoft.com
                          RT   10 wan-router.example.microsoft.com 


Description: Signature resource record. Encrypts a RRset to a signer's (RRset's zone owner) domain name and a validity interval. For more information, see RFC 2535.

owner  class  
SIG  ttl  signature_expiration  signature_inception  key_identifier  signer_name{digital_signature}


widgets.microsoft.com IN SIG 86400 19700101000000 19700101000000 49292





Description: Start of authority (SOA) resource record. Indicates the name of origin for the zone and contains the name of the server that is the primary source for information about the zone. It also indicates other basic properties of the zone. The SOA resource record is always first in any standard zone. It indicates the DNS server that either originally created it or is now the primary server for the zone. It is also used to store other properties such as version information and timings that affect zone renewal or expiration. These properties affect how often transfers of the zone are done between servers authoritative for the zone. For more information, see Managing authority records.


  • In the example below, the owner (primary DNS server) is specified as "@" because the domain name is the same as the origin of all data in the zone (example.microsoft.com.). This is a standard notation convention for resource records and is most often seen in the SOA record.

owner  class  SOA  name_server  responsible_person  
(serial_number  refresh_interval  retry_interval  expiration  minimum_time_to_live)


@   IN  SOA     nameserver.example.microsoft.com.  postmaster.example.microsoft.com. (
                               1            ; serial number
                               3600         ; refresh   [1h]
                               600          ; retry     [10m]
                               86400        ; expire    [1d]
                               3600 )       ; min TTL   [1h]


Description: Service locator (SRV) resource record. Allows multiple servers providing a similar TCP/IP-based service to be located using a single DNS query operation. This record enables you to maintain a list of servers for a well-known server port and transport protocol type ordered by preference for a DNS domain name. For example, in Windows Server 2003 DNS, it provides the means to locate domain controllers that use Lightweight Directory Access Protocol (LDAP) service over TCP port 389.

The purposes of each of the specialized fields used in an SRV resource record are as follows:

  • service  A symbolic name for the desired service. For well-known services, a reserved universal symbolic name such as "_telnet" or "_smtp" is defined in RFC 1700. If a well-known service name is not defined in RFC 1700, a local or user-preferred name can be used instead. Some widely used TCP/IP services, notably the Post Office Protocol (POP), do not have a single universal symbolic name. If RFC 1700 assigns a name for a service indicated in this field, the RFC-defined name is the only name that is legal to use. Only locally defined services can be named locally.

  • protocol  Indicates the transport protocol type. Typically, this is either TCP or UDP, although any transport protocol named in RFC 1700 can be used.

  • name  The DNS domain name referred to by this resource record. The SRV resource record is unique among other DNS record types in that it is not used to perform the search or query.

  • priority  Sets the preference for a host specified in the target field. DNS clients that query for SRV resource records attempt to contact the first reachable host of the lowest numbered preference listed here. Although target hosts have the same stated preference value, they can be tried in random order. The range of preference values is 0 to 65535.

  • weight  Can be used in addition to preference to provide a load-balancing mechanism where multiple servers are specified in the target field and are all set to the same level of preference. When selecting a target server host among those of equal preference, this value can be used to set an added level of preference that can be used to determine the exact order or balancing of selection for the target hosts used in an answered SRV query. When a non-zero value is used, servers of equal preference are tried in proportion to the weight of this value. The range of values is 1 to 65535. If load balancing is not needed, use a value of 0 in this field to make the record easier to read.

  • port  The server port on the target host that provides the service indicated in the service field. The range of port numbers is 0 to 65535, although the number is often a well-known assigned service port number, as specified in RFC 1700. Unassigned ports can be used as needed.

  • target  Specifies the DNS domain name of the host that provides the type of service being requested. For each host name used, a corresponding host address (A) resource record in the DNS namespace is required. A single period (.) can be used in this field to indicate authoritatively that the requested service specified in this SRV resource record is not available at this DNS domain name.

For more information, see the Internet draft "A DNS RR for specifying the location of services (DNS SRV)."

service.protocol.name  ttl  class  SRV  
preference  weight  port  target


_ldap._tcp._msdcs    SRV  0 0   389 dc1.example.microsoft.com
                   SRV 10 0   389 dc2.example.microsoft.com 


Description: Text (TXT) resource record. Maps a DNS domain name specified in the owner field to a string of characters in text_string serving as descriptive text. For more information, see RFC 1035.

owner  ttl  class  TXT  


example.microsoft.com.    TXT  "This is an example of additional domain name information." 


Description: Well-known service (WKS) resource record. Describes the well-known TCP/IP services supported by a particular protocol on a specific IP address. WKS records provide TCP and UDP availability information for TCP/IP servers. If a server either supports both TCP and UDP for a well-known service or has multiple IP addresses that support a service, then multiple WKS records are used. For more information, see RFC 1035.

owner  ttl  class  WKS  
address  protocol  service_list


example.microsoft.com.    WKS TCP ( telnet smtp ftp ) 


Description: X.25 (X25) resource record. Maps a DNS domain name in the owner field to a Public Switched Data Network (PSDN) address number specified in psdn_number. PSDN numbers used with this record should follow the X.121 international numbering plan. For more information, see RFC 1183.

owner  ttl  class  X25  


example.microsoft.com.    X25  52204455506

Managing core network services    Microsoft Windows 2000 Server