A Records

Table of Contents


What is an A record?

An A record maps a domain name to the IP address (Version 4) of the computer hosting the domain. Simply put, an A record is used to find the IP address of a computer connected to the internet from a name.

The A in A record stands for Address. Whenever you visit a web site, send an email, connect to Twitter or Facebook, or do almost anything on the Internet, the address you enter is a series of words connected with dots.

For example, to access the DNSimple website you enter www.dnsimple.com. At our name server there’s an A record that points to the IP address 208.93.64.253. This means that a request from your browser to www.dnsimple.com is directed to the server with IP address 208.93.64.253.

A Records are the simplest type of DNS records, yet one of the primary records used in DNS servers.

You can do quite a bit more with A records, including using multiple A records for the same domain in order to provide redundancy. Additionally, multiple names could point to the same address, in which case each would have its own A record pointing to that same IP address.

The DNS A record is specified by RFC 1035.

A record format

The structure of an A record follows the standard top-level format definition defined RFC 1035. The RDATA section is composed of one single element:

address A 32 bit Internet address representing an IPv4 address

Hosts that have multiple Internet addresses have multiple A records.

The canonical representation is:

A <address>

where <address> is an IPv4 address and looks like 162.159.24.4.

In DNSimple, the A record is represented by the following customizable elements:

Name The host name for the record, without the domain name. This is generally referred to as “subdomain”. We automatically append the domain name.
TTL The time-to-live in seconds. This is the amount of time the record is allowed to be cached by a resolver.
Address The IPv4 address the A record points to.

Querying A records

You can use dig to determine the A record associated to a domain name. The result is contained in the ANSWER section. It contains the fully-qualified domain name (FQDN), the remaining time-to-live (TTL) and the IP address.

$ dig A api.dnsimple.com

; <<>> DiG 9.8.3-P1 <<>> A api.dnsimple.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 5792
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;api.dnsimple.com.		IN	A

;; ANSWER SECTION:
api.dnsimple.com.	59	IN	A	208.93.64.253

;; Query time: 80 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Sun Jul 31 22:21:31 2016
;; MSG SIZE  rcvd: 50

Manage A records

From the DNSimple record editor, you can add, remove, and update A records.