DNS Resource Records

Resource Contents

Any answer from a DNS nameserver query takes the form of a resource record (generally referred to as an RR).
Resource records look like this: NAME TTL CLASS TYPE RDATA
NAME: The host is that which is being queried. If we were querying dns1.easystreet.com for “www.easystreet.com”, “www.easystreet.com” would be the NAME.
TTL: Time To Live is a 32-bit integer stating how long in seconds a nameserver or the user making the query should cache the results returned for this record. Values of zero in this section declare the record uncachable.
CLASS: This is assumed to be 1 or IN in all cases. Other classes (CSNet (2), BIND’s Chaos (3), MIT’s Hesiod (4)) are essentially deprecated and unlikely to be found.
TYPE: Any one of many possible RR types (RRTs). A fairly full listing of relevant TYPES can be found on IANA.
RDATA: Dependent upon RRT and described below.

Resource Record Types


TYPE RDATA Example Description
A Dotted quad Contains the IPv4 address that the domain resolves to. If there are multiple, generally a random one is chosen by the system making the query to use.
AAAA hexadecimals seperated by colons 2001:6B0:1:EA:A00:20FF:FE8F:708F Contains the IPv6 (post-experimental replacement for IPv4) equivalent of A.
NS Domain name dns2.easystreet.com. Contains the domain name a nameserver of the domain. Any domain must have at least two nameservers.
SOA Domain name of primary, domain name of hostmaster, serial, refresh, retry, expiration, default time to live dns1.easystreet.com. hostmaster.easystreet.com. ( 2003042840 ;serial (version) 14400 ;refresh period (4 hours) 900 ;retry interval (15 minutes) 604800 ;expire time (1 week) 3600 ;default ttl (1 hour) ) Start of a zone of authority. This declares a nameserver which is “authoritative” for the domain; any queries (about any domains under the authority) sent to this nameserver will be firsthand and accurate, not cached.
MX Preference number, domain name 100 smtp.easystreet.com. The domain specified is designed to deal with all email sent to NAME. Also given is a mailing priority in case one machine rejects or fails to respond to sent emails. “1” is first priority.
CNAME Domain name easystreet.com. A canonical domain name for the queried domain. The specified domain is considered equivalent to the queried domain for mailers and other programs.
PTR Domain name easystreet.com. A pointer to another domain. Similar to CNAME, except that the queried domain is not equivalent to the referenced domain.
TXT Arbitrary text "You" "should" "follow" "standards" "and" "use" "www." Descriptive text for the queried domain.
NULL Unstandardized data Space used when testing experimental DNS functions. The “NULL” record can safely be ignored by users and isn’t allowed on master servers.
MD Domain name mail.easystreet.com. Mail destination capable of acting as a mail agent and accepting mail for the domain.
MF Domain name mail.easystreet.com. Mail forwarder capable of accepting mail and sending it to another system.
HINFO CPU type string, OS type string "sun-ultra1" "unix" Host information used by some special software.
MINFO RMAILBX, EMAILBX mail.easystreet.com. mail.easystreet.com. Mailing information generally used for mailing lists. RMAILBX is the responsible mail box used for the mailing list, EMAILBX is the error mail box to which problems are sent.


easystreet.com. 3600 IN NS dns1.easystreet.com.
easystreet.com. 3600 IN NS dns2.easystreet.com.
easystreet.com. 3600 IN NS dns3.easystreet.com.
easystreet.com. 3600 IN SOA hostmaster.easystreet.com. ( 2003042840 ;serial (version) 14400 ;refresh period (4 hours) 900 ;retry interval (15 minutes) 604800 ;expire time (1 week) 3600 ;default ttl (1 hour) )
easystreet.com. 3600 IN A
easystreet.com. 3600 IN MX 100 smtp.easystreet.com.
easystreet.com. 3600 IN MX 120 mxqueue.easystreet.com.