What Is a DNS Server and How Does It Work?

The working of the internet looks simple on the surface. As a standard user, when you open a browser and search for a website, it opens immediately. But behind that opening, technical work is progressing in milliseconds within the system. This system is called DNS, and without it, the internet that we use every day cannot work.

We are writing this article to help you learn:

• What DNS is and how it works
• What a DNS server does
• Different DNS server types

Let’s start with the basics first.

What Is DNS?

DNS stands for Domain Name System. It is a translation system that translates domain names of websites into their respective IP addresses.

But why is DNS needed? Let us simplify the concept for you.

There’s one basic rule behind it, and that is the working of computers and networks. Just to remind you, computers and networks communicate using numbers, i.e., IP addresses. They do not handle items in alphabetical order.

But remembering numbers is a tough thing for us as humans. That is why the DNS system was developed: it allows us to submit queries in alphabetical order. We enter a query, e.g., a website name. DNS translates a name into numeric addresses (IP addresses), which enable our device to communicate over the internet and access a particular website.

In simple DNS works as follows:

• You type a domain name.
• Browser checks its local DNS cache.
• If no cached result exists, the Query is sent to the recursive DNS resolver.
• Resolver forwards the query to the root name server.
• Root server passes the query to the relevant TLD server.
• Lastly, the resolver query reaches the authoritative server, and it returns the IP address.
• The resolver sends the IP address back to your device, the browser connects to the web server, and loads the website.

For Your Information (FYI): The IP addresses we discussed above are public, not private. Check out the difference between a Public and a Private IP address for more details.

What Is DNS Server?

A DNS server is a computer system that stores a database of DNS information. These specialized servers are designed to respond to domain name queries by returning the correct public IP address needed to reach a website.

A DNS server acts as a directory for the Internet. When a website, e.g., example.com, is searched on the internet, the DNS server provides the IP address that allows your device to connect to the correct server. If they stop working, bad things can happen. For example:

• Websites will not load
• Emails will not be delivered
• Mobile apps may fail
• Cloud services will stop responding

How DNS Servers Work?

DNS servers work by translating a domain name into its public IP address. This translation process is referred to as DNS resolution.

Here’s how DNS servers work when you search for a domain:

• The DNS resolver will first check the cache. If you have previously visited the same website, the IP address for the domain you searched for might be stored there. If it is, the server will return with the corresponding IP address right from the cache.
• If the IP address is not in the DNS cache, a query is sent to the root server to resolve it (find the IP address).
• The root server will point the query to the TLD (top level domain) server.
• Lastly, the request is sent to the authoritative server. It is the one that holds the IP address of a domain name.

Hence, the query is resolved, and the domain name is translated into an IP address. The DNS server returns the IP address to your device so you can access the website.

Yet the process is quite technical, and it all happens in milliseconds because of DNS caching.

Types of DNS Queries

For a better understanding of DNS resolution and the things that unfold in between different DNS servers, you have to understand DNS queries.

A DNS Query is the request a DNS Client (your device) makes to a DNS server when you search for a domain name. The purpose of the query is to translate the domain name to its corresponding public IP address.

Mainly, DNS Queries are of three types:

When the lease expires, the device can:

• Recursive Query: A query is made by the client to the resolver. Resolver tries to locate a record from its existing database. If none is found in the cache, the query is forwarded to the Root Name Server. If the root name server fails to resolve the query, the resolver then queries an authoritative server until resolved.
• Iterative Query: DNS resolver repeatedly sends queries to DNS servers, from top-level DNS servers to the lowest-level Authoritative Name servers, until the query is resolved.
• Non-recursive Query: The DNS server resolves the client query using cached data.

Types of DNS Servers

Types of DNS servers are defined based on how DNS resolution is handled across the Internet. DNS uses a hierarchical model where each DNS server type performs a specific task.

When we say a client’s DNS query is resolved, it doesn't necessarily mean there is only one DNS server involved. Multiple DNS server types can be involved, each playing a specific role. The following are the four primary types of DNS servers.

1. Recursive DNS Server

When you try to open a domain over the internet, the first DNS server your device contacts is the Recursive DNS Server, also called the Recursive DNS Resolver. This server is usually provided by your internet service provider (ISP) and can also be a public DNS server. For example:

• Google DNS
• Cloudflare DNS

It is the responsibility of the recursive DNS server to find the answer to the query you searched for. Cloudflare DNS servers use a global Anycast network to improve query speed, reduce latency, and enhance privacy for public DNS resolution.

Here we would like to clarify a misconception.

Your device never talks to the root-level authoritative servers directly. It talks to the recursive resolver, which then talks to the other servers on your device's behalf.

2. Root Name Server

Root name servers are at the very top of the DNS hierarchy. They tell the DNS resolver where to find the top-level domain (TLD) servers. As per Wikipedia, there are 13 logical root name servers that range from A to M. All these 13 servers are distributed globally using Anycast.

• FYI: Anycast is a network routing method where multiple servers share the same IP address in different locations. When you connect, the network automatically routes you to the nearest or best-performing server.

Additionally, there’s one more important thing you should know. Root name servers do not know the corresponding IP addresses for domain names. They only help DNS resolvers by telling them where to go next (a TLD server based on the domain extension) to find the IP address for a domain.

3. TLD (Top-Level Domain) Name Server

Next comes the TLD servers. These are responsible for storing and managing the domain extension-related information, including generic top-level domains such as:

• .com
• .net
• .org
• .edu, etc.

And also the country-level domain extension, such as:

• .us
• .uk
• .pk
• .de, etc.

It is the responsibility of TLD name servers to forward the query from the DNS resolver they receive via the root name server to the authoritative name server associated with the domain name.

4. Authoritative Name Server

Lastly, the query reaches the Authoritative name server pointed to by the TLD server. The authoritative DNS server is the one that holds all the DNS records for a domain name and is managed by the domain owner/administrator.

The Authoritative Name Server holds all the configured DNS record types, including:

• A
• AAAA
• NS
• TXT
• MX, etc.

The IP address of the domain names resides in A or AAAA records. When the query reaches this server, it responds to the DNS resolver with the IP address from its record values, which your device then forwards to your device, and the website loads. All of this happens in milliseconds.

Public Vs Private DNS Server

When your devices need to access a website over the internet, a DNS server is required to translate a domain name into an IP address. That DNS server can be either a Public DNS server or a Private DNS Server. Here’s how a Public DNS server differs from a Private DNS server.

Public DNS Server

A public DNS server is a DNS resolver that is accessible to anyone on the internet and is often managed by third-party providers. They are accessible from anywhere on the internet, and anyone can use them by changing their device's network DNS settings.

Popular examples of public DNS servers include:

• Google Public DNS (8.8.8.8, 8.8.4.4)
• Cloudflare DNS (1.1.1.1)
• OpenDNS
• Quad9

For more, check out this list of Public DNS servers. These providers run large, global DNS infrastructures. These DNS servers come into play when you access a website publicly over the internet, as discussed above.

Private DNS Server

A private DNS server resolves DNS queries within a specific network. It is not open to the public and is fully controlled by the owner organization.

Companies and enterprises typically use private DNS servers to provide employees with access to tools and services that cannot be reached via the public internet within their internal network. These servers are created by making a separate DNS zone.

Once created, whenever a person connected to the same network searches for a query (a domain), the private DNS server checks its internal zone and replies with the required information (IP address) to resolve the query.

DNS Lookup Vs DNS Resolver

DNS Lookup is the process by which a DNS query is resolved, and record values are retrieved from a domain name's DNS configuration.

On the other hand, DNS Resolver is like a networking component, or you can say a service that acts as a carrier/service. It forwards the query to the DNS servers on the client's behalf, resolves it, and returns the results to the client.

Additionally, there’s another process called DNS Record Lookup. This process is carried out using various methods, including the DNS Lookup Tool, which helps retrieve all records configured in a domain name's DNS setup. Networking experts and web admins often use it for various purposes. For example, to verify that all record values in the DNS configuration are correct.

Wrapping Up

DNS plays a key role in how the internet works every day. It converts easy-to-remember domain names into IP addresses that computers can interpret.

When you type a website name, multiple DNS servers work together in the background to find the correct destination. Because of this system, websites load quickly, services remain accessible, and the internet operates smoothly without users noticing the complex processes behind it.

Frequently Asked Questions

What happens if a DNS server is down or Fail?

If a DNS server fails because it is down, websites, apps, and other online services will become inaccessible. The device will not be able to translate the domain name into an IP address, which means the domain will become inaccessible. In case of a technical error with one of the global DNS servers, you can switch to one of the alternate DNS servers to restore the services.

What type of information does a root DNS server contain?

Root Name servers maintain the list of TLDs (Top-Level Domains) and the IP addresses of the name servers responsible for managing each TLD. They are distributed globally via Anycast. When a client DNS query reaches the root name server, it directs the DNS resolver to the relevant TLD for resolution.

What is the main purpose of a DNS server?

The purpose of a DNS server is to make internet access usable by converting complex IP addresses into easy-to-remember domain names and help in multiple ways, including;

• Websites load correctly
• Emails reach the right servers
• Applications connect to cloud services

Is public DNS faster than private DNS?

There is no single answer to this question as it depends on the situation. Public DNS servers are faster for general browsing because they have servers worldwide. When a user enters a query, it is routed to the nearest server.

Additionally, public DNS servers have fast and efficient caching systems that help resolve queries more quickly. Private DNS, on the other hand, works inside a company's local network. They are faster at resolving internal domains by avoiding internet hops, thereby reducing lookup time.

Who manages DNS globally?

DNS servers work through a shared global coordinator. ICANN (Internet Corporation for Assigned Names and Numbers) oversees the global DNS servers. They set rules for domains and IP addresses. There are other organizations, such as the Internet Assigned Numbers Authority (IANA), that operate under ICANN and are responsible for managing root DNS zones. Additionally, some root server operators manage root DNS servers.

Is DNS the same as an IP address?

No, they are not. DNS is different from an IP address. An IP address is a numeric identifier used to identify a device online. In contrast, DNS (Domain Name System) is responsible for translating human-friendly domain names, e.g., example.com, into their corresponding machine-readable IP addresses.

How to secure DNS Servers?

You can secure DNS servers by following these basic steps:

• Use DNSSEC to protect DNS data from tampering
• Restrict access with firewalls and ACLs
• Keep DNS software updated and patched
• Disable open recursion for public servers
• Monitor logs to detect suspicious activity

These steps help prevent attacks and keep DNS reliable.