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What is a Redundant DNS Server?

June 23, 2021
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Tanya Valdez is a Technical Writer at Constellix. She makes the information-transfer material digestible through her own transfer of information to our customers and readers. Connect with her on LinkedIn.

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Secondary DNS service affords you an extra set of authoritative nameservers to answer queries for your domain. The information that is stored on both nameservers is identical. Secondary DNS allows your domain zone file to be backed up automatically and stored as a copy on a secondary server. If one provider is unreachable, the other will systematically step in to answer the queries. Since the resolvers learn the servers’ speed patterns, they can also prefer the faster resource as the initial point-of-contact for incoming queries.

How Does Redundant /Secondary DNS Work?

Having Secondary DNS is much like setting a destination on a map application on your mobile phone and letting it guide you. If there are two ways to get to the same location, it will take you through the path of “least resistance"—the one that will not only get you there but take the faster route. Secondary DNS is a mission-critical configuration that provides extra redundancy for your domain since you are able to establish a supporting set of automatically updated zone files. This is essential in bypassing DNS service outages, misconfigurations, natural disasters, and targeted attacks such as distributed denial-of-service (DDoS) attempts. 

Who Needs Redundant DNS?

Any website that generates revenue, whether it is for subscription services or through sales, would be the perfect candidate for Secondary DNS. Having the extra set of nameservers allows the traffic to be directed to either the primary or secondary DNS server helping your domain’s uptime. Without having a “backup,” your website is completely inaccessible if you have an outage, and that can cost both you and your customers money. What if your website does not generate revenue directly, but still assists in sales? The same losses would apply. For example, if you host a website for realtors or property management establishments, potential clients cannot view listings when they are in the market to purchase or rent a home. This is a loss all around that you would not want to experience. 

However, having just a primary DNS server for a domain that does not generate revenue, can also be detrimental to companies and customers alike. In the event the server is unavailable, pertinent information cannot be reached. For websites such as news outlets, possible emergency details cannot be obtained by the public. 

Did you know? Some popular healthcare organizations dedicated to providing medical information, resources, and life-saving products such as the COVID-19 vaccination, rely on only one DNS provider?

Secondary DNS can be required by some domain registrars, however, it is now best practice in the industry to configure a second service provider (SP). It is the best approach for a reason. 

How to Check Your DNS Nameservers

There are several online tools available to check your domain credentials, including your DNS nameservers. 

The DNS nameservers that are applied to the domain will display on the search results page of the lookup tool that you utilize. Here is an example of what you will see when using Whois Lookup. The DNS nameservers are shown at the bottom of the screen.

DNS Lookup tool - DNS Checker

Secondary DNS: We All Need Somebody to Lean On

Secondary DNS provides your domain with an extra set of nameservers for queries to be routed to. Rather than having one primary DNS provider to lean on, you are supported by a secondary. The DNS zone files that are stored on both can be updated to provide the most recent version of your domain so that end users will receive the intended information.

For more information on DNS zone files and primary DNS, see our related resources:

What is a Primary DNS Server

What is a DNS Zone File

5 Secondary DNS Myths Debunked 

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