DNS records

(redirected from A record)

DNS records

A DNS server contains a "zone file" for each domain, and the zone file is made up of "resource records" (RRs). The most common are described below. See DNS.

Forward DNS and Reverse DNS (A and PTR)
The Address (A) record associates a domain name or subdomain with an IP address, which is the primary purpose of the DNS system. The @ sign identifies "this domain;" for example, A @ nnn.nnn.nnn.nnn means this is the IP of this domain.

The Pointer (PTR) record provides data for reverse DNS, which is used for logging the domain name and verification purposes. Also called "inverse DNS," the PTR record is an option. See reverse DNS.

Aliasing Names (CNAME)
The Canonical Name (CNAME) record is an alias that points to other names. It is commonly used to map subdomains to the domain without having to enter the IP address again. For example, CNAME mail @ associates the mail subdomain to the this domain.

DNS Name Servers (NS)
Two Name Server (NS) records identify the authoritative DNS servers for the domain. Required for redundancy, the secondary name server queries the primary server for changes.

Mail Servers (MX)
The Mail Exchange (MX) record identifies the server to which email is directed. It also contains a priority field so that mail can be directed to multiple servers in a prescribed order.

Text Record (TXT)
A TXT record can be used for any documentation or identification purpose. It is also used to provide information to the SPF email authentication system. See SPF.

Start of Authority (SOA)
The Start of Authority (SOA) record contains the name of the primary DNS server, which must correspond to an NS record in the file.
  associate subdomain to 32-bit IP

 PTR (reverse DNS)
  associate IP address to a subdomain

 CNAME (aliases)
  associate an alias to a domain

 SOA (name of primary nameserver)

 NS (name server)
  associate a domain to a DNS server

 TXT (documentation)

 DNAME (aliases)
  associate an alias to a subdomain

 MX (mail server)
  associate mail to a mail server

 AAAA (forward DNS - IPv6)
  (1st IPv6 record)
  associate subdomain to 128-bit IP

 A6 (forward DNS - IPv6)
  (future IPv6 record)
  associate subdomain to 128-bit IP
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.
References in classic literature ?
For your lexicographer, having written his dictionary, comes to be considered "as one having authority," whereas his function is only to make a record, not to give a law.
Under this row of faint grease prints he would write a record on the strip of white paper--thus:
Wilson knew Roxy by sight, and when the duel of wits begun to play out, he stepped outside to gather in a record or two.
Breaks Although there was no report last week, it is worth recording that a record was achieved in the Gold v Albert Club match where no less than nine 20+ breaks were made; Gold's being Mike Watson (22, 23, 25), Paul Jamieson (25, 38) Roy Handley (22, 25) and Musky Handley (25) whilst the Albert Club's Alex Currie recorded a 23.
The Pirates won the pennant in 1902 with a record of 103-36 (.741), 27.5 games in front of the second-place Brooklyn Superbas.
Consequently, at least one function of the archive is to provide a record of both the original defamatory material and any consequent official response broadcast on air.
For those who are keenly interested in the ROI of the venture, it should be noted that Richard Branson, who turned a record label into a multitude of other things, including an airline, Virgin Atlantic, which set the venerable British Airways back on its heels, announced the establishment of Virgin Galactic and plans to have Rutan develop a five-seat spacecraft for tourist flights that will have a ticket price of $208,000 per ticket.
His 57 saves last season set a record that may never be broken.
Businesses are concerned that at some point in the future a Revenue Canada auditor may deny input tax credits because a record otherwise unnecessary for managing the taxpayer's business either is not retained for tax purposes or, more likely, is retained in a format that the auditor is unfamiliar with or uncomfortable accepting for audit purposes.
In their first year of existence in 1962, the Mets lost their first nine games of the season, leading Stengel to comment, "This sets up the possibility of losing 162 games, which would probably be a record in the National League, at least."
But he had set a record when Merrrill called him out as well.