Background

A 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 come in a fairly wide variety of types in order to provide extended name-resolution services.
Source: RFC 1035, Section 3.2, Page 11

DNS Resource Record Fields

Field Length Description Details
NAME 255 Bytes
or less
The name of the node to which this resource record pertains.

Blank Name - A record that has nothing in the 'name' field gets used for all requests being made to the base domain. (Same as Parent)

@ Symbol - Some DNS management systems allow the use of the @ symbol in the 'name' field instead of the 'Blank Name' value. The '@' symbol substitues the current value of the $ORIGIN.

* Symbol (Wildcard) - This symbol is used as an indicator that the record named '*' should be used in place of any record that isn't specified. Consider it a catch all.
TTL 4 Bytes The TTL (Time To Live) is a positive values of a 32 bit signed integer that specifies the time interval that the resource record may be cached before the source of the information should again be consulted. Zero values are interpreted to mean that the RR can only be used for the transaction in progress, and should not be cached. For example, SOA records are always distributed with a zero TTL to prohibit caching. Zero values can also be used for extremely volatile data.
CLASS 2 Bytes Two bytes containing one of the RR CLASS codes. (RFC 1035, Section 3.2.4). Example: "IN" for Internet    more_vert
TYPE 2 Bytes Two bytes containing one of the RR TYPE codes.    more_vert
RDLENGTH 2 Bytes An unsigned 16 bit integer that specifies the length in bytes of the RDATA field.
RDATA Variable A variable length string of bytes that describes the resource (Resource Data). The format of this information varies according to the TYPE and CLASS of the resource record.

RR Syntax

name ttl class type rdata {One or more fields as described in the resources RDATA format}

Examples

Snippets from a fictitious 'yourdomain.com' domain zone file

Typical 'A' Record Entries

;
;   Zone records
;
www 3600 IN A 104.16.45.99
3600 IN A 104.16.45.99
* 3600 IN A 98.137.11.163
When querying for www.yourdomain.com or yourdomain.com, you will receive the answer of 104.16.45.99
When querying for api.yourdomain.com, you will receive the answer of 98.137.11.163 (Due to the wildcard '*' entry and ‘API’ has not been explicitly defined)

See Also




This content was last updated on December 10, 2020
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