DNS Explained

DNS Explained

The purpose of the DNS (Domain Name Server) system is to give client computers a means of translating host names (ex. wpmututorials.com) into IP (Internet Protocol) addresses. In a typical day of working my browser(s) submits hundred of queries to my DNS servers to get the IP address of the web sites I have requested. Once the browser has the IP address it submits my request to that IP address.

DNS did not exist in the early days of the Internet. Originally, what each system admin did was maintain a local list of host names and the IP address associated with each host (in the early 90's I was one of those system admins). When it was a small number of hosts this worked ok. But, as the number of hosts being accessed grew, maintaining the local list became regular maintenance. Every time a service was moved from one host to another, everyone who accessed the service had to update their hosts file.

When you are setting up your DNS, what you are doing is adding the lookup information for your domain to the Internet's DNS system. The types of records that you may have to add are:

  • NS - This identifies a DNS server that is an authoritative server for your domain. Other DNS servers will query this one to get the domain's current DNS records.
  • MX - This is a record to say where the domain's mail server can be found,
  • CNAME - Canonical name - This is essentially an alias that points one domain name to another domain name.
  • A - This is an address record and specifies the IP address that the domain can be found at.

The note to keep in mind with DNS is that it is separate and distinct from web, mail, ftp, etc. server setup.

  • Martin
    Posted at 09:58h, 25 May Reply

    Thanks for the article. Would you say it’s generally better to use the registrar’s DNS or the webhost’s DNS?

    I suspect the answer is “it depends”, but I wonder about pros and cons.


  • Barry
    Posted at 11:15h, 25 May Reply

    I tend to use neither. 🙂 I’d suggest using an external DNS provider and one, if at all possible, with geographically spread DNS servers.

    As a DNS server is the key for a user getting to your site, it makes sense to have as reliable a system as possible.

    Also, you should never (in my opinion) use your hosts DNS servers. If your hosts internet connection goes down for any period of time and you want to redirect your domain to a “holding page” or a backup site on another server, then you need that DNS accessible and external to the host.

    • Martin
      Posted at 11:21h, 25 May Reply

      @ Barry
      Thank you! That make a lot of sense.

  • Ron
    Posted at 13:03h, 25 May Reply

    If you are using hosting in North America with a larger hosting company, the host’s DNS servers are likely to be spread out geographically. For example one of our servers is a futurehosting VPS. Futurehosting has 2 DNS servers in each of their datacentres which are all in different US states. We can access to our DNS through any of the datacentres.

  • Dr. Mike Wendell
    Posted at 15:01h, 25 May Reply

    Back in the old days, you were actually required to have your DNS servers off and away from your servers. Things changed when everybody started having their own websites. And, to be honest, if your server is down, having DNS up and running isn’t going to matter since there’s no where for your visitors to go.

    For our clients, we run the local server as primary DNS and use a pair of VPS elsewhere for secondary and Tertiary DNS.

  • Edwards
    Posted at 16:47h, 26 May Reply

    Well said Mike. Not sure about other efficient ways.

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