I took an in depth look at how the Domain Naming System (DNS) works in this article. In this new series of articles I’m going to explore the 10 most common types of DNS records. In this first installment of DNS Records, I’ll discuss Address Records (A Record). To prep you for the discussion, I’m going to give a brief overview of the type of DNS Servers and discuss Time To Live (TTL). If you own a domain and/or have hosting through a host provider, you can view and manage your DNS records at your registrar (typically) by selecting your domain then select manage DNS. The image below is from a domain I own that also has a website on it via GoDaddy GoCentral, but all the other records are default settings and have not been altered by me.
Types of DNS servers
There are three types of DNS Servers:
- DNS Resolver receives DNS queries.
- DNS Root Server is at server that extracts the TLD and routes the user to the TLD name server which then provides IP address and other details to route the user to the appropriate location. There are presently 13 DNS Root Servers world wide.
- Authoritative DNS Server holds all the up-to-date information for a particular domain. Every domain has an Authoritative DNS Server.
Time To Live (TTL) defined
If you login to your where your domain name is registered or your website is hosted and make a change to your DNS records, you’re making a change to your Authoritative DNS Server. Your DNS records are (typically) cached on all the other servers – which is why you get the message that it may take 24-48 hours to update certain DNS records. If you’re not familiar with caching, you can think of that as the local version of a shared file, where it takes time for shared files to propagate to multiple computers – thus, some shared files may not have the latest version. Caching improves performance. The TTL is the time period a server keeps record/s on file before requesting the most up-to-date version from the Authoritative DNS Server. TTL is typically expressed in seconds, for example if your TTL is set to 3600 – that is 3600 seconds or 1 hour.
Now that we have a general understanding of the types of DNS Servers and TTL, let’s take a look at the first of the series of DNS Record types – Address Mapping Record, or A Records.
The Address Mapping Records (A Record) is commonly referred to as DNS host record. In a sentence, the A Record stores the hostname for the IPv4 (Internet Protocol Version 4) addresses. Let’s briefly define two terms, hostname and IPv4. Simply stated, a hostname is a label that is assigned to a device connected to a computer network and that is used to identify the device in various forms of electronic communication. An example of a hostname is jasonofflorida.com or google.com. Internet Protocol Version 4 is the fourth version of the Internet Protocol that is used to route traffic on the internet – IPv4 was deployed to production in 1983 and most internet traffic is still routed via IPv4 – although the next version and successor (IPv6) is used today. Internet Protocol is governed by Request For Comments memoranda (RFC) 791.
Basic examples of A Records:
- If I wanted google.jasonofflorida.com to display the google search page (google.com), I would enter a record that looks like:
- Name: google.jasonofflorida.com
IPv4 Address: 184.108.40.206*
- A better real life example, is if I wanted to point a subdomain of my webiste (for example, store.jasonofflorida.com) to my Amazon store, I would enter the appropriate A Record to do that.
- Name: google.jasonofflorida.com
*note: google’s IPv4 Address is 220.127.116.11. You can look this information up via a NS Lookup tool.
In this scenario above, when I typed google.jasonofflorida.com into a browser, then the google home search page would appear. To be completely honest, I can’t think of a single reason to do this, but it served as a good example.
Next in the series I will discuss IP Version 6 Address record (AAAA Record).