How Domain Name Servers (DNS) Work

By: Marshall Brain, Nathan Chandler & Stephanie Crawford  | 
worker draws DNS diagram
An IT worker draws a diagram of the Domain Name System (DNS) on a digital whiteboard. GodfriedEdelman/Getty Images

The internet and the World Wide Web are wild frontiers that rely on computer languages, codes, and web browsers to find and share data and information. One of the most fundamental instruments of the internet is the Domain Name System, or DNS. (Although many people think "DNS" stands for "Domain Name Server," it really stands for "Domain Name System.")

DNS is a protocol within the set of standards for how computers exchange data on the internet and on many private networks, known as the TCP/IP protocol suite. Its purpose is vital, as it helps convert easy-to-understand domain names like "" into an Internet Protocol (IP) address, such as that computers use to identify each other on the network. It is, in short, a system of matching names with numbers.


The DNS concept is like a phone book for the internet. Without this kind of way finding system, you'd have to resort to much more complicated and esoteric means to sift through the virtual open plains and dense cities of data strewn across the global internet ... and you can bet that it wouldn't be nearly as much fun, especially since there are now hundreds of millions of domain names [source: VeriSign].

Without DNS servers, the internet would shut down very quickly. But how does your computer know what DNS server to use? Typically, when you connect to your home network, internet service provider (ISP) or WiFi network, the modem or router that assigns your computer's network address also sends some important network configuration information to your computer or mobile device. That configuration includes one or more DNS servers that the device should use when translating DNS names to IP address.

So far, you've read about some important DNS basics. The rest of this article dives deeper into domain name servers and name resolution. It even includes an introduction to managing your own DNS server. Let's start by looking at how IP addresses are structured and how that's important to the name resolution process.


DNS Servers and IP Addresses

You just learned that the primary job of a domain name server, or DNS server, is to resolve (translate) a domain name into an IP address. That sounds like a simple task, and it would be, except for the following points:

  • There are billions of IP addresses currently in use, and most machines have a human-readable name as well.
  • DNS servers (cumulatively) are processing billions of DNS queries across the internet at any given time.
  • Millions of people are adding and changing domain names and IP addresses each day.

With so much to handle, DNS servers rely on network efficiency and internet protocols. Part of the IP's effectiveness is that each machine on a network has a unique IP address in both the IPV4 and IPV6 standards managed by the Internet Assigned Numbers Authority (IANA). Here are some ways to recognize an IP address:


  • An IP address in the IPV4 standard has four numbers separated by three decimals, as in:
  • An IP address in the IPV6 standard has eight hexadecimal numbers (base-16) separated by colons, as in 2001:0cb8:85a3:0000:0000:8a2e:0370:7334. Because IPV6 is still a very new standard, we'll concentrate on the more common IPV4 for this article.
  • Each number in an IPV4 number is called an "octet" because it's a base-10 equivalent of an 8-digit base-2 (binary) number used in routing network traffic. For example, the octet written as 42 stands for 00101010. Each digit in the binary number is the placeholder for a certain power of two from 2 to 27, reading from right to left. That means that in 00101010, you have one each of 21, 23 and 25. So, to get the base-10 equivalent, just add 21 + 23 + 25 = 2 + 8 + 32 = 42.
  • There are only 256 possibilities for the value of each octect: the numbers 0 through 255.
  • Certain addresses and ranges are designated by the IANA as reserved IP addresses, which means they have a specific job in IP. For example, the IP address is reserved to identify the computer you're currently using. So, talking to is just talking to yourself [sources: Cisco, Lammele].

Web servers and other computers that need a consistent point of contact use static IP addresses. This means that the same IP address is always assigned to that system's network interface when it's online. To make sure that interface always gets the same IP address, IP associates the address with the Media Access Control (MAC) address for that network interface. Every network interface, both wired and wireless, has a unique MAC address embedded in it by the manufacturer.

Now, let's look at the other side of the DNS equation: domain names.


Domain Names logo
The logo is displayed on a cardboard shipping envelope from Amazon. is the domain name for Amazon in the United Kingdom. nkbimages/Getty Images

If we had to remember the IP addresses of all our favorite websites, we'd probably go nuts! Human beings are just not that good at remembering strings of numbers. We are good at remembering words, however, and that is where domain names come in. You probably have hundreds of domain names stored in your head, such as:

  • — our favorite domain name
  • — one of the most used domain names in the world
  • — a popular EDU name
  • — a three-part domain name using the country code UK

You'll recognize domain names as having strings of characters separated by dots (periods). The last word in a domain name represents a top-level domain. These top-level domains are controlled by the IANA in what's called the Root Zone Database, which we'll examine more closely later [source: IANA]. There are more than 1,000 top-level domains, and here are some of the most common:


  • COM — commercial websites, though open to everyone
  • NET — network websites, though open to everyone
  • ORG — non-profit organization websites, though open to everyone
  • EDU — restricted to schools and educational organizations
  • MIL — restricted to the U.S. military
  • GOV — restricted to the U.S. government
  • US, UK, RU and other two-letter country codes — each is assigned to a domain name authority in the respective country

In a domain name, each word and dot combination you add before a top-level domain indicates a level in the domain structure. Each level refers to a server or a group of servers that manage that domain level. For example, "howstuffworks" in our domain name is a second-level domain off the COM top-level domain.

An organization may have a hierarchy of sub-domains further organizing its internet presence, like "" which is the BBC's domain under CO, an additional level created by the domain name authority responsible for the U.K. country code.

The left-most word in the domain name, such as www or mail, is a host name. It specifies the name of a specific machine (with a specific IP address) in a domain, typically dedicated to a specific purpose. A given domain can potentially contain millions of host names as long as they're all unique to that domain.

The "http" part stands for Hypertext Transfer Protocol and is the protocol by which information is sent by the user to the website she is visiting. Nowadays, you're more likely to see "https" which is a sign the information is being sent by secure protocol where the information is encrypted. This is especially important if you're providing a credit card number to a website [source: EasyNews].

Later, when we look at how to create a domain name, we'll see that part of registering a domain requires identifying one or more name servers (DNS servers) that have the authority to resolve the host names and sub-domains in that domain. Typically, you would do this through a hosting service, which has its own DNS servers. Next, we'll look at how these DNS servers manage your domain, and how DNS servers across the internet work together to ensure traffic is routed properly between IP addresses.


The Distributed System

Website address
The "www" part of the domain address stands for "World Wide Web" and means you're looking for something online (as opposed to another part of the internet, like mail). It's less important than it used to be to include those three letters in an address. Hemera Technologies/Getty Images

Every domain has a domain name server handling its requests, and there is a person or IT team maintaining the records in that DNS server's database. No other database on the planet gets as many requests as DNS servers, and they handle all those queries while also processing data updates from millions of people every day. That's one of the most amazing parts of DNS — it is completely distributed throughout the world on millions of machines, managed by millions of people, and yet it behaves like a single, integrated database!

Because managing DNS seems like such a big job, most people tend to leave it to the IT professionals. However, by learning a little bit about how DNS works and how DNS servers are distributed across the internet, you can manage DNS with confidence. The first thing to know is what the purpose of a DNS server is on the network where it resides. A DNS server will have one of the following as its primary task:


  • Maintain a small database of domain names and IP addresses most often used on its own network, and delegate name resolution for all other names to other DNS servers on the internet.
  • Pair IP addresses with all hosts and sub-domains for which that DNS server has authority.
DNS servers routing requests
When you enter a URL into your web browser, your DNS server uses its resources to resolve the name into the IP address for the appropriate web server.

DNS servers that perform the first task are normally managed by your internet service provider (ISP). As mentioned earlier, the ISP's DNS server is part of the network configuration you get from DHCP as soon as you go online. These servers reside in your ISP's data centers, and they handle requests as follows:

  • If it has the domain name and IP address in its database, it resolves the name itself.
  • If it doesn't have the domain name and IP address in its database, it contacts another DNS server on the internet. It may have to do this multiple times.
  • If it has to contact another DNS server, it caches the lookup results for a limited time so it can quickly resolve subsequent requests to the same domain name.
  • If it has no luck finding the domain name after a reasonable search, it returns an error indicating that the name is invalid or doesn't exist.

The second category of DNS servers mentioned above is typically associated with web, mail and other internet domain hosting services. Though some hardcore IT gurus set up and manage their own DNS servers, hosting services have made DNS management much easier for the less technical audience.

A DNS server that manages a specific domain is called the start of authority (SOA) for that domain. Over time, the results from looking up hosts at the SOA will propagate to other DNS servers, which in turn propagate to other DNS servers, and so on across the internet.

This great web of DNS servers includes the root name servers, which start at the top of the domain hierarchy for a given top-level domain. There are hundreds of root name servers to choose from for each top-level domain. Though DNS lookups don't have to start at a root name server, they can contact a root name server as a last resort to help track down the SOA for a domain.

Now that you know how DNS servers are interconnected to improve the name resolution process, let's look at how you can configure a DNS server to be the authority for your domain.


Creating a New Domain Name

person shopping online
Having a memorable domain name is important if you're a shopping website. skaman306/Getty Images

When you want to create a new domain name, you need to do the following:

  • Use the Whois database to find a unique domain name that isn't yet registered. There are several sites that offer free Whois database searches, such as Network Solutions. If the search comes up empty, you know the domain name is available.
  • Register the domain name with a registrar. There are a lot of registrars to choose from, and some offer special prices for registering the COM, NET, and ORG versions of a domain at the same time, for registering for two or more years, or for hosting the domain with the same company.
  • If you're hosting the domain at a different company than your registrar, configure the registrar to point your domain name to the correct host name or IP address for your hosting company (see information below about A records) [source: Wilson and Randall].

Whether your SOA is somewhere else or on your own system, you can extend and modify your DNS settings to add sub-domains, redirect e-mail and control other services. This information is kept in a zone file on the DNS server. If you're running your own server, you'll probably need to manually edit the zone file in a text editor. Many registrars today have a web interface you can use to manage DNS for your domain. Each new configuration you add is called a record, and the following are the most common types of records you can configure for your DNS server [source:].


  • Host (A) — This is the basic mapping of IP address to host name, the essential component for any domain name.
  • Canonical Name (CNAME) — This is an alias for your domain. Anyone accessing that alias will be automatically directed to the server indicated in the A record.
  • Mail Exchanger (MX) — This maps e-mail traffic to a specific server. It could indicate another host name or an IP address. For example, people who use Google for the e-mail for their domain will create an MX record that points to
  • Name Server (NS) — This contains the name server information for the zone. If you configure this, your server will let other DNS servers know that yours is the ultimate authority (SOA) for your domain when caching lookup information on your domain from other DNS servers around the world.
  • Start of Authority (SOA) — This is one larger record at the beginning of every zone file with the primary name server for the zone and some other information. If your registrar or hosting company is running your DNS server, you won't need to manage this. If you're managing your own DNS, you can peek at tips for doing so using this article on the structure of a DNS SOA Record [source: Burch].

The following is an example of what a zone file might look like for those who are editing it directly in a text editor. Note that the center column (second item on each line) includes a record type from those listed above. When you see an "@" in the left column, it means that the record applies in all cases not otherwise specified:

@ NS

@ NS

@ MX 10 mail

mail A

vip1 A

www CNAME vip1

Typical users will probably get the most use out of MX and CNAME records. The MX records allows you to point your mail services somewhere other than your hosting company if you choose to use something like Google Apps for your domain. The CNAME records let you point host names for your domain to various other locations. This could include setting to redirect to, or setting up a dedicated game server with its own IP address and pointing it to something like


DNS is Constantly Evolving

You should understand that DNS is not a static concept. In late 2018, ICANN finally rolled out new security features for DNS. In short, those changes affected the cryptographic keys used in the Domain Name System Security Extensions (DNSSEC) protocol, known by techies as the root zone key signing key (KSK). The security improvements were necessary, says ICANN, because of the way networks are rapidly changing and expanding, in part due to the Internet of Things, which brings millions of new interconnected devices into the internet's fold [source: Cooney].

Those safety measures are incredibly important because criminal-minded hackers often try to tap into the DNS system to steal personal information or simply wreak havoc, for example, in attacks like DNS hijacking. That means defense-minded computer users and IT professionals alike must stay up to date on preventative measures to prevent DNS poisoning attacks and denial-of-service attacks, among others [sources: Greenberg].



Whats is a DNS?
DNS stands for Domain Name System and is considered to be the phonebook of the internet. A DNS connects URLs with the right IP addresses.
What does a DNS do?
A DNS provides a way to match a URL to the IP of a particular website.
Can I use an 8.8 8.8 DNS?
This is the public DNS server of Google and basically means that Google is the provider of the DNS and is responsible for the maintenance of the service. This DNS can be used by anyone on the internet.
Is switching your DNS safe?
Changing a DNS setting to OpenDNS servers is considered to be safe, is totally reversible and does not harm the network or the PC.
What does DNS mean on your phone?
Every connection made with the internet is dependent on a DNS, and that also includes your phone. To enable a private DNS on your phone, go to Settings > Network and Internet > Advanced > Private DNS > enter the URL of your private DNS service as the hostname and click save.

Lots More Information

Related Articles
More Great Links

  • Bluehost Web Hosting. "Parked Domain Definition." (Nov. 5, 2018)
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  • Cisco. "IP Addressing and Subnetting for New Users." August 10, 2016. (Nov. 5, 2018)
  • Cooney, Michael. "ICANN's Internet DNS Security Upgrade Apparently Goes off Without a Glitch." Network World. Oct. 12, 2018. (Nov. 5, 2018)
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