Constellix Labs
Constellix Lab: 5 Minute Lessons September 19, 2016

What’s the difference between ANAME, AAAA, A, and CNAME records?

This week we are introducing our new weekly feature, Constellix Labs.

Once a week we will answer a question or troubleshoot a common issue users have when managing their DNS… all in five minutes or less!

If you’re new DNS record management, you were probably a little overwhelmed when you saw that Constellix lets you to use over a dozen different record types. This week, we are going to teach you the differences between the four main DNS record types. And then we will teach you how you can use these different records to improve your domain’s performance.

Before continuing, we recommend that you already have a basic understanding of how DNS works. Check out this free ebook DNS for Newbies from our sister company, DNS Made Easy.

 

A Records

A records are the most commonly used record type. If you have ever set up a website, you most likely configured an A record before. These records are the most basic form of a DNS record and almost all other record types we will discuss are based off of A record functionality.

When you set up an A record, you will specify an FQDN (Fully Qualified Domain Name) to be pointed to an IP address. If you are creating a website, then the IP address will usually be given to you by your DNS registrar when you purchased your domain name.

A records also have the ability to be pointed to the root of a domain. For example: if your website is at www.example.com, then the root of your domain would be example.com. The root can also be called a “naked domain” and is usually represented by an @ symbol when you are configuring a record. When you are configuring your records in Constellix DNS, your domain name will automatically be added to your “record name”, so all you have to specify is the subdomain or “@” for the root.

You can learn how to set up an A record here.

 

AAAA Records

This is where things start to get a little more complicated. AAAA records are very similar to A records in that they point a domain name to an IP address. The catch is, the IP address isn’t a typical IPv4 address like: 255.255.255.0. Instead, AAAA records point to IPv6 addresses like: 2001:0db8:85a3:0000:0000:8a2e:0370:7334.

Not too long ago, we realized the world would eventually run out of IPv4 addresses, so IPv6 addresses were developed. These longer addresses allow for an astronomical number of unique addresses and won’t be in short supply for a very long time. Since we developed a new address type, we also had to create a new record type to support it –hence the addition of AAAA records.

You can learn how to configure AAAA records here.

 

CNAME Records

CNAME records, also known as alias records, point a hostname to another hostname or FQDN. These records are typically used to point multiple hosts to a single location, without having to specifically assign an A record to each host name. For example: if you moved your blog from news.example.com to blog.example.com, then you would use a CNAME record. CNAME records can also be used to point a hostname to another domain or external hostname.

To resolve a CNAME record, the name server must behave slightly differently than it would with a normal query of another record type. When a name server looks up a name and finds it is a CNAME record, it replaces the name with the canonical name (the target of the CNAME) and looks up the new name. In a sense, a CNAME lookup performs two queries to reach the final resolution.

There are a few limitations you should consider before configuring a CNAME record. First, you should only use a CNAME record if there are no other records for that hostname. Second, CNAME records cannot be used for a root record.

You can learn how to configure CNAME records here.

 

ANAME Records

You may have noticed that some of the records we have already covered have a few limitations. We needed a record that could point a hostname to another hostname or FQDN but could also represent to root record. Essentially a CNAME record for the root of a domain. RFC requirements wouldn’t allow this, so instead we developed our very own ANAME records.

These records allow you to point the root of your domain to a hostname or FQDN. This functionality has also allowed ANAME records to work seamlessly with CDNs (Content Delivery Network) because they allow for multiple dynamically updated IP addresses to be authoritative for a domain in many different locations.

ANAME records allow you to do so much more with your DNS configurations when you use them in Constellix DNS. You can see the full list of advantages and performance benefits here.

 

Other Record Types

You may remember that Constellix DNS allows you to work with about a dozen different record types. We will explain a few more of the most common record types in next week’s episode of Constellix Labs.

 

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