What is a DNS Server?

Domain Name System (DNS) Diagram
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The Domain Name System (DNS) is a technology standard for managing names of public Web sites and other Internet domains. DNS technology allows you to type names into your Web browser like lifewire.com and your computer to automatically find that address on the Internet. A key element of the DNS is a worldwide collection of DNS servers.

A DNS server is any computer registered to join the Domain Name System.

A DNS server runs special-purpose networking software, features a public IP address, and contains a database of network names and addresses for other Internet hosts.

DNS Root Servers

DNS servers communicate with each other using private network protocols. All DNS servers are organized in a hierarchy. At the top level of the hierarchy, so-called root servers store a complete database of Internet domain names and their corresponding IP addresses. The Internet employs 13 root servers that have become somewhat famous for their special role. Maintained by various independent agencies, the servers are aptly named A, B, C and so on up to M. Ten of these servers reside in the United States, one in Japan, one in London, UK and one in Stockholm, Sweden.

More: List of DNS Root Servers (iana.com)

How DNS Works

The DNS is a distributed database system. Only the 13 root servers contain the complete database of names and addresses.

All other DNS servers are installed at lower levels of the hierarchy and maintain only certain pieces of the overall database.

Most lower level DNS servers are owned by businesses or Internet Service Providers (ISPs). For example, Google maintains various DNS servers around the world that manage the google.com, google.co.uk, and other domains.

Your ISP also maintains DNS servers as part of your Internet connection setup.

DNS is based on the client/server network architecture. Your Web browser functions as a DNS client (also called a DNS resolver) and issues requests to your Internet provider's DNS servers when navigating between Web sites.

Whenever a DNS server receives a request not in its database (such as one for a geographically distant or rarely visited Web site), it temporarily behaves as a DNS client. The server (acting on behalf of the original client) automatically passes that request to another DNS server or up to the next higher level in the server hierarchy. This process continues until the request eventually arrives at a server that has the matching name and IP address in its database - passing all the way to the root level if necessary - and the response flows back through the chain of DNS servers to the original client.

You can use publicly available DNS tools can be used to search for information related to Internet domains. Professional network administrators use these same basic tools on business networks.

DNS Servers and Home Networking

Computers on your home network locate a DNS server through their Internet connection setup properties.

Internet providers supply their customers the public IP addresses of primary and backup DNS servers, which are normally automatically set on a home network gateway device via DHCP. Alternatively, a home network administrator may also elect to use one of the free Internet DNS services.

You can find the current IP addresses of your DNS server configuration via several methods:

  • on the configuration screens of a home network router
  • on the TCP/IP connection properties screens in Windows Control Panel (if configured via that method)
  • from ipconfig or similar command line utility

More: How to Change DNS Server Settings on Home Computer Networks