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Acronym. Domain Name Server.

A server which translates a Domain Name into one or more IP Addresses.

When using a Web Browser, DNS takes the part between "http://" and the first slash "/" and converts it into an IP Address, which is a very large number which uniquely identifies a web server on the internet.

For example for the web address:


DNS takes the term www.example.com and converts it into an IP address:

DNS Applications

DNS is used as the primary way of converting names on the internet to addresses. Any application which accesses the internet uses DNS first to find a server. Because DNS is the first step used in any internet transaction, it is the target of security breaks. |

DNS is used by the following applications:

  • Web Browser
    • To resolve the host portion of a URL, and any additional URL on a page.
  • Email Program
    • To resolve your email server's IP Address, and to determine the Mail Exchanger for outbound email.
    • Recently, to retrieve a DomainKeys record to authenticate a sender of an email
  • FTP Program
    • To resolve the host name of a remote FTP server
  • Operating System
    • To resolve the name of your vendor's servers for Software Update ... (Mac OS X), or Windows Update ... (Windows)
  • Any application which checks for software updates
    • To resolve the name of the vendor's host server

DNS Tools

On Linux, FreeBSD, Mac OS X, or any variant, you can use a command line tool (using iTerm, Terminal, xterm, or some similar shell tool) to perform DNS on the fly using the host command:

> host www.example.com
www.example.com has address

On Windows, to perform DNS requests, go to the Start Menu, then Run ..., and type in nslookup:

Default Server: acumen
> www.example.com Server: acumen Address:
Non-authoritative answer: Name: www.example.com Address:

You can just enter the name you wish to resolve and it will output the response from your local DNS server.

More info

  • Also known as Name Server or one word: Nameserver
  • See Name Server on Wikipedia