Zone transfer: What is it and how does it work?

Today we will talk about zone transfer. First, we will explain its purpose and how it functions. Then we will explore what a zone file is, and for the final note, we will see the zone transfer vulnerability’s effects. So, let’s start.

Zone transfer: Definition

Duplicating DNS records from the Master DNS zone to the Backup DNS zone is the procedure known as zone transfer. This gives you the option to duplicate your DNS records on various alternative name servers. You will have higher availability as a result of finishing the transfer if one of the name servers fails. Additionally, faster DNS resolution will be advantageous if you run a worldwide website with users from all over the world and numerous presence locations (PoPs).

Another crucial point to remember is that your website won’t be harmed if a name server goes down for whatever reason (for example, maintenance or a DDoS attack). It will continue to be reachable and available for your guests.

You may want to consider completing a zone transfer to numerous Secondary zones if you are in charge of a global website and wish to speed up Domain Name System resolution. This method can distribute your DNS information (DNS records) across many Points of Presence (PoP).

How does it function?

It would help if you duplicated all modifications and changes you make to your Primary DNS zone to the Secondary DNS servers. However, there are guidelines for when and how to transfer these changes. The SOA (Start of Authority) document is responsible for it happening. The Slave DNS servers’ refresh rate is carried by it. The period (in seconds) that Slave DNS servers will wait before asking the Master DNS server for the SOA record to check if it has been updated is what this term means. When a DNS zone file’s serial number changes, Slave DNS servers are informed to update their copies of the zone file via a DNS transfer.

What is a zone file?

A DNS zone file, commonly referred to as the master file (RFC 1035), is a straightforward text file that contains all DNS resource records (RR) for a specific DNS zone. The principal name server is where you may find this DNS zone file. The primary DNS zone, which is housed in the significant name server, is where any changes to the domain name are made. The DNS zone files have been modified. Therefore, the zone file’s content will vary if DNS RR is added or removed.

Zone transfer vulnerability’s effects

No authentication is provided by DNS zone transfer. Therefore, a DNS server can be asked for a copy of the complete zone by any client or a person pretending to be a client.

This implies that absent some form of protection, anyone can obtain a list of every host for a specific domain, providing them with a wide range of potential attack vectors.


Let’s review. The procedure by which DNS copies zone files or specific DNS records from a Primary name server to one or more Secondary name servers we known it as DNS zone transfer. Furthermore, you won’t be able to deploy it properly until you have a strong understanding of what it is.

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