What is Domain Name System (DNS) and how do I use it?

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DNS is responsible for specifying where your internet resources are located. These resources can be web servers, mail server, ftp servers, remote access servers, or any other resource your company offers that you want to be accessed with a a Fully Qualified Domain Name (FQDN). 

A FQDN is a path to a network or internet resource. An example is mail.nvthost.com which is a FQDN to our mail server and webmail interface. Your company may need to set up FQDN such as vpn.yourcompany.com for VPN access. The purpose of creating these entries is to make it easier to remember these resouce locations than remembering the IP addresses. It also helps with administration since you can change the IP of your mail server at the DNS server if all clients are using a FQDN to access the server. Otherwise you would have to update everyone with the new IP address.

DNS also helps by directing e-mail to the mail server responsible for your domain. When someone sends an e-mail to an address at your domain their client asks the DNS server for your domain for a list of mail servers that handle mail for your domain. When your mail is hosted by your ISP or hosting provider the DNS server points to their mail server. When you host your own e-mail on a standard mail server or an exchange server then the DNS server points directly there. These records that point to your domain's mail servers are called Mail Exchanger (MX) records.

Some free DNS tools are:
  • IpTools.com: Tools to query DNS servers and perform diagnostic tests.
  • MxToolbox.com: Tools to check MX record setup and perform blacklis lookups.
  • IntoDNS.com: Performs full domain DNS query.

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