What is a Secondary DNS zone?
The Secondary DNS zone represents a read-only copy of the DNS data (DNS records)of the Primary (Master) DNS zone. You could find it also called Backup or Slave DNS zone. It is very important to note that for the various DNS records, for instance, A, AAAA, MX, TXT records, and many more, it is not possible to add them directly into the Secondary DNS zone.
The only method for the Secondary DNS zone to obtain the DNS data is by getting them from the Primary (Master) DNS zone of the DNS server. For that purpose, it is necessary a process called DNS zone transfer to be completed.
The Backup DNS zone can serve in several ways, yet one of the main ideas for creating it is for backup. That way, if, for some reason, your Primary DNS zone is not operating, that won’t bother you. Your Backup DNS zone is going to assist in such situations and answer the requests thanks to its copy.
Redundancy: In case your Primary DNS zone is incapable of answering, the Slave DNS zone will provide redundancy. If there is no Secondary DNS zone, if the primary DNS zone fails, your website is going to become unavailable, and users won’t be able to access your content.
Build a reliable DNS management: DNS servers that store the DNS zones could become victims of security threats. The one that is most commonly used is Distributed Denial of Service attack (DDoS attack). By setting up a DNS provider with DDoS protection and placing your Slave DNS zone there, you could protect yourself from malicious DDoS attacks.
Distributing the load: When you add a Slave DNS zone, you could provide a faster response to DNS queries.
DNS zone transfer – Types
The process called DNS zone transfer is an easy and simple task to complete. It makes a duplicate of the DNS data (DNS records) created in the Primary DNS zone to the Secondary DNS zone.
There are two types of DNS zone transfer that you could make:
- Full zone transfer (AXFR zone transfer). With this type, you could make a copy of all the DNS records from the Primary DNS zone to the Secondary DNS zone. It is great to use it when you haven’t updated the Secondary for a long period of time, and you want to be sure that everything is up to date. Another case when it is commonly used is for a new Backup DNS zone, and you have to import the entire information.
- Incremental zone transfer (IXFR zone transfer). This type is very useful when you want to update only the latest changes in your DNS information from your Primary DNS zone to the Slave DNS zone. That way, only the modifications will update, and it is going to use fewer network resources. It is easy and practical!