I am starting a small series over Domain Name System records management. This series will focus on what particular DNS records mean, and how to use them. While many functions exist for DNS records, this series will focus on their basic functions from a Website owner’s perspective.
This is the first blog in this series, so I will begin by explaining what a domain name is and end by explaining A-Records. These will be our building blocks and will be referenced in other posts in the series.
The Domain Name
What exactly is a domain name? Well, Wikipedia will tell you it’s an “identification string that defines a realm of administrative autonomy, authority or control on the Internet.” So, what does this mean for you if you want to host a website? Essentially, it means a name for your website in the simplest terms.
For example, sharepointspace.com is a domain name. A common misconception is that the www prefix is a part of the domain name. In actuality, this is a sub-domain and not your domain name and not interchangeable with your domain name without specific actions being taken to make it so. The best way to think of this is that if sharepointspace.com is your domain name, then anything in front of it is a sub-domain, including www.
Some examples of sub-domains are below to help illustrate this point include elough.sharepointspace.com, www.sharepointspace.com, home.portal.sharepointspace.com, or *.sharepointspace.com.
(elough, www, and portal are all subdomains of sharepointspace.com while home is a sub-domain of portal.sharepointspace.com. *.sharepointspace.com is a way this information is commonly represented.)
Purchasing Your Domain Name
When you purchase a domain name, you also own any sub-domain that you care to place in front of said domain. You will purchase domain names through a Domain Name Registrar. Go-Daddy is probably the most famous one you’ve heard of. While many Domain Name Registrars (such as Go-Daddy) also offer hosting, these are not “hand-cuffed” services.
Many companies only offer domain name registration or hosting, and many can offer both. Regardless of what services you choose to purchase, you will at least need to purchase a domain name to start, and where you purchase this is considered your Domain Registrar. Your Registrar will typically have a DNS control panel where you edit the DNS for the domain and sub-domains.
Domains’ and sub-domains’ DNS is managed in the same location, although depending on your Registrar, the interfaces can vary quite a bit. Most will use the same terminology, so if you know the basics, you should be able to navigate any User interface efficiently.
Let’s introduce the first and arguably most important DNS record, the A-Record:
As mentioned earlier this is arguably the most important DNS record. The A-Record in a nutshell is a pointer, (as most DNS records are), but more specifically a pointer for web traffic. The A-Record associates an IP address with a domain, (or sub-domain) name. The A-Record is different from other records as it is the “primary” pointer for traffic. When you type a URL from your home browser, a query is sent out to DNS servers for this A-Record so that you can be directed to the appropriate IP address/location. An example of this can be seen below:
In this picture you can see that the sub-domain, elough.sharepointspace.com, is pointing to an IP address, (220.127.116.11), and is an A-Record, (Type).
The TTL is a property of almost all DNS records and is simply how long that record “lives” on a particular name server before it expires and polls for an updated record. This affects, (in a minor way), what is called propagation. DNS changes typically take 1-48hours to propagate globally. (The actual number most DNS providers will give is 24-48hrs, but it is my experience that DNS usually propagates in a couple of hours).
Since it would not be practical to have these records only stored on one DNS server, (as it would mean people looking for your site would need to travel halfway around the world to resolve your domain name), propagation copies your DNS records to other public DNS server’s worldwide. The caveat of this is that when you make a change, it is not immediately recognized globally.
How can you test your DNS for your own domain? Many tools exist for this, but I will focus on two that you can run from your command prompt.
Ping: Probably the most used command line tool ever, simply pinging your domain name should resolve to an IP.
As you can see from above, the IP address in parenthesis is the same from the A-Record. This is how you can check what your domain name resolves to. If you get a “could not find host” error then you do not have an A-Record properly configured for the domain, or there is a problem with your DNS services or local Internet Service.
NSLookup: This tool is much more advanced and has a wide array of capabilities.
While I will not go into much detail as that would take away from the focus of this article, it is an extremely valuable tool. You can determine specific DNS records and query a specific name server which allows you to diagnose DNS problems from several angles. To get more information about NSLookup syntax, you can type nslookup /? from a command prompt as seen below:
For more information, check out this article from Microsoft Support entitled Using NSlookup.exe.
I will work on addressing the other record types in upcoming posts. As always thank you for reading!