A secondary Domain Name System (DNS) server gives domain name owners additional authoritative nameservers to answer domain queries. Every domain needs a DNS server so users who wish to visit it can do so. That DNS server is called a “nameserver.” Your go-to DNS server is the primary DNS server, and it contains information that is identical to those stored in your secondary server.

You can thus think of a secondary DNS server as your backup. If one is unreachable, the other automatically steps in to answer queries. That way, your website is always accessible.

Other interesting terms…

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Before we go into an in-depth discussion about secondary DNS servers, let’s tackle what the DNS does first.

What Is the DNS?

The DNS is an Internet service that translates domain names into IP addresses. You see, computers direct users to the sites they want to visit based on their IP addresses. That said, you can think of the DNS as the Internet’s phonebook. You can look for a person’s address and phone number through it. In this scenario, the person’s name is the domain name, and his/her address and phone number translate to the IP address. Without the DNS, users won’t be able to access the sites they want to visit.

The following diagram shows how a DNS server works:

  1. When you type a domain name into your web browser, your computer translates it to an IP address. Your request gets sent to a DNS recursive resolver, which finds the site’s IP address.
  2. The DNS recursive resolver asks the root server for the site’s correct top-level domain (TLD) server.
  3. The root server responds to the resolver with the address of the TLD server. If you wish to visit threatmedia[.]com, for example, the resolver is directed to the .com TLD server, which keeps a list of every .com website.
  4. The TLD server (.com nameserver in this case) points to the authoritative server that contains threatmedia[.] com’s corresponding IP address.
  5. The authoritative server checks if it has the correct data.
  6. If it does, it sends the IP address to the computer.
  7. Once that is done, the user can access the website.
DNS process
Source: https://www.businessinsider.com/what-is-a-dns-server

How Does a Secondary DNS Server Work?

Having primary and secondary DNS servers is like getting all possible routes to your intended destination on your mobile phone map app. The app guides you on which road to take to get to where you want to go as fast as possible when you’re driving.

That’s what primary and secondary DNS servers do. Whichever can answer queries faster does so.

Who Needs Secondary DNS Servers?

All companies that maintain websites to generate revenue or operate need secondary DNS servers. These backups allow them to direct traffic (transactions for sales sites or requests for production platforms) to the server that would produce results faster.

If the primary DNS server fails or malfunctions, the secondary one can take over. All buyers can go on with their purchases. And all employees can continue working despite an outage.

What Are the Benefits of Using Secondary DNS Servers?

Using secondary servers gives organizations at least two advantages, namely:

  • Redundancy and resiliency: Having a single DNS server translates to a single point of failure. If it fails or gets compromised, potential site visitors can no longer access your portal. A secondary DNS server makes that occurrence less likely.
  • Load balancing: A secondary DNS server shares the load—incoming domain requests—so the primary one doesn’t get overloaded, resulting in a denial-of-service (DoS). Primary and secondary DNS servers get roughly equal traffic, ensuring business continuity.

Can Your Primary and Secondary DNS Servers Come from the Same Provider?

The quick answer is yes, but that may not be the ideal setup.

Do you remember the distributed denial-of-service (DDoS) attack on Dyn in 2016? Dyn is one of the largest DNS service providers worldwide, which was hit by the controllers of the Mirai botnet. A considerable number of its customers, including Twitter, Netflix, and CNN, went offline for some time. Imagine if Dyn managed your primary and secondary servers. You’d have no choice but to wait for it to restore its services to get your business up and running again. But if another company provides your secondary DNS server, you can continue operating despite the DDoS attack.

You’ve seen how vital secondary DNS servers are. If you want to ensure business as usual despite system malfunctions and cyber attacks, you should probably start subscribing to a secondary DNS service.