DNS - Domain Name System

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The Domain Name System (DNS) translates Internet domain and host names to IP addresses and vice versa. DNS automatically converts between the names we type in our Web browser address bar to the IP addresses of Web servers hosting those sites.

How DNS Works

DNS follows a client/server network model. Client send requests to and receive responses from DNS servers. Requests containing a name that result in an IP address being returned from the server are called forward DNS lookups. 

Requests containing an IP address and resulting in a name, called reverse DNS lookups, are also supported. DNS implements a distributed database to store this name and address information for all public hosts on the Internet. It assumes IP addresses do not change (are statically assigned rather than dynamically assigned).

The DNS database resides on a hierarchy of special database servers. When clients like Web browsers issue requests involving Internet host names, a piece of software called the DNS resolver (usually built into the network operating system) first contacts a DNS server to determine the server's IP address. If the DNS server does not contain the needed mapping, it will in turn forward the request to a different DNS server at the next higher level in the hierarchy. After potentially several forwarding and delegation messages are sent within the DNS hierarchy, the IP address for the given host eventually arrives at the resolver, that in turn completes the request over Internet Protocol.

DNS additionally includes support for caching requests and for redundancy. Most network operating systems support configuration of primary, secondary, and tertiary DNS servers, each of which can service initial requests from clients.

For more information -  Introduction to the Domain Name System (DNS)

Setting Up DNS on Personal Devices and Home Networks

Internet Service Providers (ISPs) maintain their own DNS servers and use DHCP to automatically configure their customer's networks, Automatic DNS server assignment relieves households of the burden of DNS configuration. Home network administrators are not required to keep their ISPs settings, however. Some prefer to use one of the available public Internet DNS services instead. Public DNS services are designed to offer better performance and reliability over what a typical ISP can reasonably offer.

Home broadband routers and other network gateway devices store primary, secondrary and tertiary DNS server IP addresses for the network and assign them to client devices as needed. Administrators can choose to enter addresses manually or obtain them from DHCP.  Addresses can also be updated on a client device via its operating system configuration menus.

For more information - How to Change DNS Server Settings on Home Computer Networks

Being a distributed system, issues with DNS can be intermittent and difficult to troubleshoot. Clients can still connect to a local network when DNS is broken, but they will be unable to reach remote devices by name.

When a client device shows DNS server addresses for it indicates an issue with configuration.

See also - Troubleshooting Home Network Router Problems

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