What Is Secondary DNS Server?


Angela Bailey

A secondary DNS server is an important component of a domain name system (DNS) infrastructure. It acts as a backup to the primary DNS server and helps to ensure the availability and reliability of DNS services.

What is DNS?

DNS is a protocol that translates domain names into IP addresses. It allows users to access websites and other internet resources by using human-readable domain names, such as example.com, instead of numeric IP addresses, like

The DNS system is hierarchical and distributed, with multiple servers responsible for different domains. When you enter a domain name in your web browser, it sends a query to a DNS server to obtain the corresponding IP address.

The Role of Primary DNS Server

The primary DNS server is the first point of contact for resolving domain names within a specific zone or domain. It stores the authoritative data for that zone, including information about the IP addresses associated with domain names.

When a user requests to access a website, their device sends a query to the primary DNS server. If the primary server has the necessary information in its cache, it responds with the IP address immediately. However, if it doesn’t have the information or cache has expired, it needs to fetch it from another source.

Why Do We Need Secondary DNS Servers?

A secondary DNS server comes into play when the primary server fails or becomes unavailable for any reason.

If the primary DNS server goes down or experiences connectivity issues, users won’t be able to access websites associated with that particular zone until it’s restored. This can lead to significant downtime and frustration for users.

To prevent such scenarios, organizations implement secondary DNS servers as backups.

Benefits of Secondary DNS Server

  • Redundancy: A secondary DNS server provides redundancy by maintaining a copy of the zone data. If the primary server fails, the secondary server can still respond to DNS queries, ensuring uninterrupted service.
  • Load Distribution: Secondary servers can share the DNS query load with the primary server, reducing the burden on a single server and improving overall performance.
  • Improved Resilience: Having multiple DNS servers enhances system resilience and reduces the risk of service disruption due to hardware failure or network outages.

How Secondary DNS Server Works

In a typical setup, the primary DNS server transfers zone data to one or more secondary servers at regular intervals. This process is known as zone transfer or AXFR (Authoritative Transfer).

The secondary DNS servers store a copy of the zone data received from the primary server. They periodically check for updates from the primary server and synchronize any changes made to the zone.

When a user’s device sends a query for a domain name, it can reach either the primary or secondary DNS server. Both servers have identical copies of the zone data and can respond with accurate IP addresses.

In Conclusion

A secondary DNS server plays a crucial role in ensuring high availability and reliability of DNS services. It acts as a backup for the primary server, providing redundancy, load distribution, and improved resilience.

By incorporating secondary DNS servers into their infrastructure, organizations can minimize downtime and provide uninterrupted access to their websites and online services.

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