Differences Between A and CNAME Records #

The A and CNAME records are the two common ways to map a hostname (“name”) to one or more IP addresses. There are important differences between these two records.

Understanding the differences #

The [A record](https://support.dnsimple.com/articles/a-record) points a name to a specific IP. If you want blog.dnsimple.com to point to the server 185.31.17.133 you’ll configure:

blog.dnsimple.com.     A        185.31.17.133

The [CNAME](<https://support.dnsimple.com/articles/cname-record>) record points a name to another name instead of to an IP. The CNAME source represents an alias for the target name and inherits its entire resolution chain.

How we use them #

Let’s use an example:

blog.dnsimple.com.      CNAME   aetrion.github.io.
aetrion.github.io.      CNAME   github.map.fastly.net.
github.map.fastly.net.  A       185.31.17.133

We use GitHub Pages, and we set blog.dnsimple.com as a CNAME of aetrion.github.io, which is a CNAME of github.map.fastly.net, which is an A record pointing to 185.31.17.133. This means blog.dnsimple.com resolves to 185.31.17.133.

Which one to use #

An A record points a name to an IP. A CNAME record can point a name to another CNAME or to an A record.