What is Backup (Slave) DNS?

Backup DNS explained.

Backup DNS is also frequently called Slave DNS, and it holds a copy of all the information for a domain, including DNS records. That copy is received right away from the Master or Primary DNS. You are not able to perform any modification, and it acts only for storing the data. In case you desire to make some additional changes to the data, you should make them in the Primary DNS. Then they are going to propagate to the Slave DNS as well.

Backup DNS is essential if you require your domain to be available constantly. In some cases, your Primary DNS server could be down. For instance, the reason could be maintenance or an attack, and then your Slave DNS is going to respond to queries. Additionally, it is very beneficial, and it is going to make your online strategy a winner in terms of redundancy, uptime, speed, etc. 

What is the difference between Backup DNS and Primary DNS?

Let’s explain it step by step. First, each DNS zone can have only one primary DNS server, an authoritative one, for storing the information about the DNS zone. Moreover, it is the entrance for the administrator that is in charge of maintaining that particular zone. Only on the primary DNS server is it possible to make adjustments or modifications to maintain the zone. Furthermore, it is how it becomes the origin for the other servers. 

So, Backup DNS could be one or several servers that are linked to a primary. The purpose is for these servers to be positioned in various and strategic points all around the world for your organization. In order to receive the information from the primary, Slave DNS servers are performing zone transfer. The goal is to mirror the DNS records.

It is a good option to choose a separate DNS provider from the one which is hosting the Primary DNS to establish the Backup DNS. The reason for that is simple. That way, you limit the chances of failures affecting your website’s performance, such as an attacked server, downtime, and so on. Moreover, in the meantime, you are increasing redundancy.

Every DNS server could operate as a Primary DNS or Secondary DNS. A Primary DNS server for a particular zone could serve simultaneously as a Backup DNS for another zone.

Why should you use it? 

There are three main reasons to use a Backup DNS:

  1. The Secondary DNS boosts network performance. When you have many points of presence (PoPs), they are capable of serving you to build a load balancing network. That way, you can handle the traffic and distribute it among the various DNS servers. Additionally, you will provide a quicker response, and the weight on your Primary DNS server is going to be less. 
  2. You have a backup copy of the DNS records. In case the Primary DNS server is down for some reason and it is not able to respond to queries, you still have a working copy of the DNS data and avoid any kind of downtime.
  3. With Secondary DNS, you can resist attacks. The most apparent reason is to hold a network of Slave DNS servers that are able to resolve queries in case your primary DNS server is down. Your customers are going to have a normal user experience, thanks to this backup.

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Author: Dominic

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