Recursive DNS is a process where a DNS resolver queries multiple DNS servers to retrieve the IP address of a domain name, ensuring the client receives the correct IP address for their requested website.
The recursive DNS server continues this process, querying from the root server down to the authoritative server, until it finds the specific IP address for the domain.
In this article, we will discuss what recursive DNS is, how it works, and the differences between authoritative and recursive DNS.
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- Recursive DNS servers request answers from all records and return with a “not found” response if records aren’t found
- Authoritative DNS servers request answers from existing records and refer you to another server if records aren’t found
- Recursive DNS servers offer users improved performance and better control, but they also present security risks
What Is a Recursive Query in DNS?
Recursive queries are a type of DNS (Domain Name System) query that retrieves DNS records for a client from a specific domain or subdomain.
When making a recursive query, it is up to the name server to determine if it has enough information available in its cache or from other authoritative sources before responding with an answer.
If it cannot find what was requested, then a “not found” message will be returned instead.
Iterative vs Recursive DNS Queries
Iterative queries are a type of DNS query that allows the client to request an answer from the name server. The name server may either respond with the requested information or refer the client to another authoritative source for more information.
Recursive queries are different from iterative ones because they require the name server to provide an answer if one is available, or else return a “not found” message if it cannot find what was requested.
Recursive DNS Query Example
Let’s say you are trying to find the IP address for a website called “example.com”.
The first step would be to send out a request to your local name server asking it if it is aware of the domain in question.
If not, the name server will then check its cache and see if there is any record that matches what was requested.
If nothing can be found, then the name server will start sending requests upstream until it finds either an authoritative answer or a “not found” message from another source further up in the hierarchy (such as the root name server).
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Authoritative vs Recursive DNS Servers
| Authoritative | Recursive | |
| Type of Query | Iterative | Recursive |
| Answers Requested | Existing Records | All Records |
| Action if Record Not Found | Refer to Another Server | Return “Not Found” Response |
- Authoritative DNS servers contain information about a domain, including IP addresses. They respond to requests for this information from clients and other name servers.
- Recursive DNS is a type of query where the server must provide DNS records or come back empty-handed. It does not refer the client to another server as with iterative queries. Instead, it searches through its records until it finds an answer or determines that the requested record does not exist.
Who Uses a Recursive DNS Server?
Recursive DNS servers are usually used by large organizations that need to be able to quickly and reliably resolve domain names.
By using a recursive server, they can provide fast and accurate answers to clients without having to rely on other name servers or wait for replies from multiple sources.
Who Uses an Authoritative DNS Server?
Authoritative DNS servers are typically used by ISPs, web hosting companies, and domain registrars. They provide answers to queries about a specific domain name from their records.
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Advantages of Recursive DNS
- Improved performance as the name server does not need to refer the client to another name server
- Reduced latency due to faster responses from recursive queries
- Increased security as the end user can be sure of their connection’s authenticity
- Greater control over content delivery by allowing organizations to cache answers from authoritative sources and serve them directly without referring clients elsewhere
Risks Associated with Recursive DNS
Recursive queries are used when a client wants an answer from a name server and does not want to wait for another name server to respond.
This can lead to potential security issues, as attackers may be able to take advantage of a vulnerable system by spoofing answers or using malicious software.
Recursive DNS Servers and DNS Amplification Attacks
A recursive DNS server will always respond to a query, regardless of whether it has the answer or not. This can lead to potential problems, as attackers may use this feature to initiate what is known as a “DNS amplification attack”.
In this type of attack, an attacker sends out multiple requests for information from vulnerable name servers, and the resulting responses are amplified in size due to the number of requests sent.
This can overwhelm the target system with traffic and cause it to become unresponsive or crash altogether.
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Recursive DNS Servers and DNS Cache Poisoning Attacks
A recursive DNS server can receive and process requests from multiple clients. It does this by caching the responses, which are then sent to the client as an answer.
This means that if a malicious user poisons the cache with incorrect information, it can disrupt any clients using the affected name server.
Final Word: Find the DNS That’s Right for You
So, what is recursive DNS? Recursive DNS is a type of Domain Name System query that requires the name server to provide an answer or not.
It contrasts with an iterative and authoritative DNS query, where the name server will either respond with the answer, or it will refer the client to another name server that may have more information.
The Best Website Builders and Best Web Hosting services are here to help you with whatever DNS you use, so make sure you use one when setting up your website.
Next Steps: What Now?
- Use the information in this article to decide what type of DNS you’d like to use
- Implement your chosen DNS on your site with the Best Website Builders and Best Web Hosting services
Learn More About DNS
- What Is a DNS? A Simple Guide to the Web’s Routing System
- What Is SOA Record in DNS? SOA Records Explained
- What Is SRV Record in DNS and How Does It Impact Your Website Hosting?
- What Is PTR Record in DNS? A Comprehensive Guide
- Guide to What Is TXT Record in DNS for Newbies
- What Type of DNS Record Is Used for Email Servers? A Introductory Guide
- What Is AAAA Record in DNS: Basic Guide to Web Navigation
- What Is a CNAME: A Thorough Introduction to DNS Management
- What Is Domain Propagation and How Does it Work?
- What Is an A Record? Exploring the Backbone of DNS
