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What is Authoritative, Recursive DNS Server & How it works

What is Authoritative and Recursive DNS Server

What is DNS ?

The Domain Name System (DNS) is one of the most essential parts of the Internet’s infrastructure. We cannot remember the IP addresses of all the websites that we use on a daily basis. So, In that case By using DNS, you can connect to any website without having to know the website’s IP address. In simple, Dns service will allow to translate domain names into IP addresses and vice versa.

What is a Recursive DNS Server ?

You might have been able to guess what a recursive DNS server does by its name. (It recurses, which means that it refers back to itself).

Recursive DNS nameservers are responsible for providing the proper IP address of the intended domain name to the requesting host.

Example : when You make a request to a website from your browser, Then Host or Computer will then make a request to recursive DNS server to find the IP address associated with the website.Assume that your operating system (OS) and Web browser do not already have a response cached. From there, the recursive server will check to see if it has a cached DNS record from the authoritative nameserver, and still has a valid time to live (TTL). If the recursive server does not have the DNS record cached, it begins the recursive process of going through the authoritative DNS hierarchy, which I will explain further down in this post.

What are Authoritative DNS Server ?

Authoritative DNS nameservers are responsible providing answers to recursive DNS nameservers with the IP “mapping” of the intended website. The authoritative nameservers’ responses to the recursive nameservers contain important information for each domain, such as corresponding IP addresses and other necessary DNS records.

How Authoritative & Recursive DNS Server Works ?

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Working of Authoritative & Recursive DNS Server

For Better Understanding of How both of the nameservers interact with each other

1. Client Computer

Imagine that, You are at your computer and you want to search for a image. So, you type www.google.com into your Web browser to go to Google. However, your computer doesn’t know where the server for www.google.com is located.

2. Recursive DNS nameserver

  1. Your computer sends a query to a recursive DNS nameserver to locate the IP address of the website for you. The recursive DNS nameserver is now assigned the task of finding the IP address of the website you are searching for.
  2. If the recursive DNS nameserver does not already have the DNS record cached in it’s system, it will then query the authoritative DNS hierarchy to get the answer. Remember, Each part of a domain like www.google.com has a specific DNS nameserver that is authoritative.

3. Root Server (“.”)

Recursive DNS Server go at the top of the tree i.e.Root Server (“.”) and It first asks the root domain nameservers (“.”) for the IP address of the TLD server. in this case, “.com” (for google.com). Basically, Root domain nameservers know the IP addresses of the authoritative nameservers that handle DNS queries for the Top Level Domains (TLD) like “.com”, “.edu” or “.gov”. There are Total 13 root dns servers by Standard.

[Note: Every domain has an hidden “.” at the end that designates the DNS root nameservers at the top of the hierarchy.]

4. Top Level Domain (TLD)

Afterwards, it asks the authoritative server for “.com”, where it can find the “google.com” domain’s authoritative server. Then “google.com” is asked where to find “www.google.com”.

5. Authoritative DNS server of (Google.com)

Once the IP address of (“Google.com”) is known for the website it will goes back to our Recursive dns server with IP and TTL Value and Cache it in our server.

6. Recursive DNS Server

Then the recursive DNS server responds to your computer with the appropriate IP address. Now, At last you can search images for all day long.

DNS Querry (Overview)

DNS works in Reverse Manner, let’s Take a Example of (“Google.com”)


  1. Root Servers (“.”).
  2. Top Level Domain (TLD) also known as (1st Level Domain).
  3. Domain Name is also known as (2nd Level Domain).
  4. Host or Subdomain

This is all about Dns like authoritative dns serverRecursive DNS Server and How DNS works.


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