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What is a Recursive DNS server?

When you browse the internet, you don’t write IP addresses to go to the pages you want; you just write the domain. In the “backstage”, every request that you do, passes through a DNS query. It first goes to your internet provider’s Recursive DNS server. If it can’t find in the cache, the information needed, it will continue to other recursive servers until it gets to an Authoritative DNS server who can give the IP address of the required domain. Basically, it is a name server, that is a middle-man between you, the user, and the Authoritative DNS server.

Recursive DNS server explained

The Recursive DNS server called, also commonly DNS resolver, has the important responsibility of seeking requested data and responding to users’ DNS queries.

In computing, when we talk about recursion, it is clearly associated with a technique that aims to solve a particular problem. In addition, that involves a program or solution that continuously repeats itself until it reaches the desired goal.

A Recursive DNS server is positioned to function in the middle between the Authoritative DNS server and the end-users that initiate DNS requests. So, each time a user desires to visit and explore a particular website, it types its domain name into the address bar of the browser. From there, the Recursive DNS server receives the request and starts searching for the IP address (IPv4 or IPv6) that corresponds to the domain name. Shortly after the required IP address is found, the DNS resolver returns to the user’s device and provides the needed information. Then the browser on the device (smartphone, laptop, computer, etc.) of the user is able to connect and load the desired website. 

The number of available Recursive DNS servers all over the world is significant. However, the most popular among them are the ones of the Internet service providers (ISP).

Tasks of the Recursive DNS server

The role of the DNS resolver is to complete one of the following tasks:

1. Checks if the IP address is stored in the cache memory. There is a certain period of time, pre-defined by the domain’s owner called Time to Live or TTL. It says for how long the Recursive server can hold the information. If it is still there, it will return the answer fast and won’t take further actions.
2. Searches for the IP address elsewhere. If it is not in the cache, it will continue the searching process until it gets to an Authoritative server which has the information.

How does it work?

The Recursive DNS server takes a very important role in the DNS resolution process. As we mentioned earlier, it operates between the user and the Authoritative DNS server. Yet, it completes several crucial tasks. Let’s summarize how it operates and what actions it performs in this vital process: 

  • The DNS resolver is the one that obtains the DNS query from the user.
  • It then asks the Root server about the location of the TLD (Top Level Domain) server.
  • The Recursive queries the TLD (Top Level Domain) server for information about which is the accountable Authoritative DNS server for the precise domain.
  • It makes a request to the Authoritative DNS server responsible for the particular domain. 
  • The Resolver gets back to the user and provides the requested data.
  • It caches the DNS information for further use.

Recursive DNS server

The existence of Recursive DNS servers is crucial. This is because they support the Authoritative DNS servers, which would not otherwise be able to handle the workload created by themselves. Additionally, DNS Resolvers distribute the load of the huge number of user requests and make the resolution of domain names way easier.

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Vulnerabilities

Cybercriminals are well aware of the importance of Recursive DNS servers. Unfortunately, they managed to use their vulnerabilities and initiate different malicious attacks. Some of the DNS resolvers are public, which makes them an easy target. Attackers often use DNS spoofing attacks or execute DDoS attacks in order to shut the servers down directly.

  • Recursive DNS servers and the amplified attacks

DNS Amplified Attacks are a very common threat on the Internet. They exploit the public Recursive DNS servers to generate high traffic and to damage the target.

  • Public (Open) recursive DNS

To leave your Recursive DNS server public is dangerous. Such devices are with minimum security and visible IP address. This means that anyone, including cyber-criminal, can easily access it and later use it as a botnet device to amplify their next attack.
Many of the network administrators don’t know their recursive servers are open, and this can lead to severe problems. If you doubt about your DNS server, you can check it on this page: http://openresolverproject.org

  • Oversized packets

A threat that some of the attackers take advantage of is manipulating the query packets. They send multiple queries to recursive servers, but with a modified IP addresses, directing all of the generated traffic towards the victims. They use many servers, and if the traffic is high, they can crush the victims’ servers.

Can you have safe Recursive DNS servers?

Yes, it is possible to secure your servers. We recommend you to use our Private DNS servers. They are hidden from the public eye and still have all of the premium features like TTL management, Cloud domains, Secondary DNS, SOA Settings and Hourly statistics
You don’t need to get all of them. You can strategically choose just a few of them where you most need them.

Conclusion 

The Recursive DNS servers are a fundamental component of the global network Internet and the DNS (Domain Name System). The role they play in the DNS resolution process is significant. DNS resolvers simplify and manage to balance the load of numerous DNS requests daily!

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Tags: , , , , , , , , , , Last modified: December 22, 2022
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