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
184.108.40.206. This means that a request from your browser to
www.dnsimple.com is directed to the server with IP address
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:
<address> is an IPv4 address and looks like
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 220.127.116.11 ;; Query time: 80 msec ;; SERVER: 18.104.22.168#53(22.214.171.124) ;; 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.