What is a DNS server?

Key takeaways:

• DNS servers translate easy-to-remember domain names into complex Internet Protocol (IP) addresses.
• When you type a website address, it goes through a step-by-step process called the DNS lookup. This involves several types of servers working together to find and deliver the needed information.
• DNS servers are prone to getting hacked or having wrong information, so it’s important to have security measures in place. These will help keep websites running smoothly and protect against cyberattacks.

Have you ever wondered why IP addresses still exist when we can simply use a website’s domain name? Computer systems still need IP addresses to get us to the pages we want to visit.

So, you might ask, “How do computers understand what we search for when all we use are web addresses?” We have DNS servers to thank for that.

In this article, we’ll explain what a DNS server is and its role in the Domain Name System (DNS). We’ll also cover the different types of DNS servers and the common causes of DNS server issues.

What is a DNS server?

A DNS server matches a domain name with its corresponding IP address to direct users to the website they’re trying to access. For example, if you’d like to visit sites like Domain.com, you only need to type www.domain.com in the search bar instead of 172.64.145.59 (Domain.com’s IP address).

DNS servers make internet surfing easier for humans by allowing us to use human-readable web addresses instead of a string of random numbers. Additionally, DNS servers optimize overall internet performance. They manage website traffic by spreading user requests across multiple servers to prevent overloading and slowdowns.

What are the types of DNS servers?

The four kinds of DNS servers are the recursive DNS server, root name server, top-level domain (TLD) name server, and authoritative DNS server. Each server plays a different role in retrieving the correct IP address, which is the goal of the DNS lookup process.

How do DNS servers work during a DNS lookup process?

Recursive DNS server

A recursive DNS server, also called a DNS resolver, answers a DNS query sent to it by a browser whenever a user searches for a site.

During a typical DNS lookup, the resolver communicates with other DNS servers to find the information needed to resolve a DNS request. Think of it as a librarian who goes through various catalogs and shelves to find the book you’re looking for.

The first server it asks is the root name server, which operates at the highest level of the DNS hierarchy.

Root name server

Once a root name server receives a query, it directs the request to the designated TLD name server based on the website’s domain extension.

For instance, if the site is www.domain.com, the root name server forwards the query to the .com TLD server.

TLD name server

A TLD name server contains data about the authoritative DNS servers for domain names that use its specific extension. When it receives a DNS request, the data it stores enables the designated TLD server to direct or forward the query to the correct authoritative DNS server for that domain.

Authoritative DNS server

An authoritative DNS server holds a domain name’s DNS records, which include information like its IP address. When a query reaches this server, it provides the recursive DNS server with the correct IP address.

Finally, the recursive resolver sends the IP address back to the browser. The browser then uses it to connect with the requested website.

What does DNS caching do?

DNS caching improves website loading speeds by allowing DNS resolvers to retrieve IP addresses from local storage instead of performing new DNS lookups.

The way it works is that after every DNS resolution, a recursive resolver keeps the information in its cache for a specific duration, known as the Time to Live (TTL).

When a user requests a website, the resolver checks its cache first. If the translation exists and the caching time limit hasn’t expired, the recursive resolver delivers the stored IP address. However, if the information exists but is no longer within its TTL, the recursive DNS server starts a fresh DNS lookup and caches the new data.

It’s important to note that the TTL exists to ensure that cached information remains updated. Without it, whenever web servers modify DNS records, the resolver provides users with incorrect data.

What causes DNS server issues?

Several factors, such as DNS attacks and DNS record issues, can prevent DNS servers from functioning properly. It’s important to be aware of these common problems to address them accordingly.

DNS attacks

Cybercriminals launch various DNS attacks by manipulating the DNS lookup process. This interception allows them to cause issues for both users and website owners.

One of the most common DNS attacks is DNS spoofing. Hackers execute this kind of attack using DNS cache poisoning and DNS hijacking. Both methods redirect users to malicious sites, which these attackers control, to steal sensitive data and funds or install malware on devices.

DNS cache poisoning happens when malicious actors trick a DNS resolver into storing the wrong IP addresses in its cache. As a result, the resolver delivers false information to users. Alternatively, in DNS hijacking, cybercriminals change a legitimate domain’s DNS settings to lead its visitors to a fake site.

To prevent DNS attacks, it’s best to employ the Domain Name System Security Extensions (DNSSEC) protocol and use DNS filtering services. These security tools offer site owners added protective layers to safeguard their webpages.

Incorrect or missing DNS records

A recursive resolver fails to answer a DNS query correctly if a domain’s DNS records are incorrect or missing. This issue causes numerous inconveniences to the affected parties.

Visitors get frustrated when websites don’t load or when they can’t connect. This leaves them with the impression that the site is unreliable, which can hurt a company’s reputation.

Businesses can also lose money as inaccurate DNS records make it harder for search engines to index their webpages. As a result, customers fail to find their sites in search results.

Website owners or administrators should check their DNS records with their hosting company or DNS provider. They should ensure that all the addresses and names are correct and that information, such as A records, AAAA records, CNAME records, and MX records, are accurate.

Primary DNS server failure

A primary DNS server is a domain’s authoritative DNS server. It contains original copies of that specific domain’s DNS records. When this server crashes or is compromised, the DNS resolver can’t retrieve the information it needs, which makes the website inaccessible.

To avoid such an outcome, administrators create a secondary DNS server to act as a backup. If the primary becomes unavailable, the secondary handles DNS requests until the former is restored.

Keep your site accessible for DNS servers

DNS servers are important for translating human-readable domain names into IP addresses to give us smooth UX as we browse the internet. This translation process is called a DNS lookup and is executed by four DNS servers, namely the recursive DNS server, root name server, TLD name server, and authoritative DNS server.

Unfortunately, DNS servers are vulnerable to cyberattacks and are prone to various issues. Perform best security practices like using DNSSEC and setting up secondary DNS servers to secure your domain.

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