If you could have an x-ray of the Internet or any other network, you could see how servers are the keystone for them to work. The amount of them and the tasks they comply with are vital for these systems’ existence. 

What does a Primary DNS server mean?

It’s called Primary DNS server or Master DNS server. These names indicate its importance since it’s the source of all the original data for a specific DNS zone and its corresponding domains. A Primary DNS server is responsible for storing all the DNS records for its DNS zone. Therefore, every time a record (or more) requires a change, edition, or to be deleted, that can only be made in the original source, the Primary DNS server.

How does the Primary DNS server work?

This fact grants the Primary DNS server a place on top of other servers as the authoritative one. Thus, every single modification made on this server will be propagated to the rest of the servers to be updated. Besides, since it holds the IP addresses, among many more domain’s DNS records, its role is vital for the DNS resolution process to be completed.

Clearly, there’s no one but many Primary DNS servers. Referring to them in plural is correct since there are many different DNS zones and many networks. But talking about a specific DNS zone, it can have just one Primary DNS server. The servers besides the Primary are usually Secondary DNS servers. They are added to hold extra copies of the zone data to provide redundancy and keep the online availability of the domain.

Secondary DNS servers don’t allow modifications to the DNS records (A record, MX record etc.). The copy they hold is only readable, not editable.

Why do you need a Primary DNS for DNS resolution?

DNS resolution is about getting the corresponding IP address for a requested domain name to be loaded. 

Let’s see a case with only one nameserver for a domain name:

When a domain name is requested, a process of searching its corresponding IP address gets triggered. This request is taken by a recursive server that will execute the search. First, it will go to the root server to ask which TLD server is responsible for the requested domain. Once the root server points to the right TLD server, the recursive will ask this last about the authoritative server in charge of the requested domain. And here, for sure, you are getting who that authority is. Yes, a Primary DNS server! The recursive server will ask the corresponding IP address to the authoritative. It will be supplied, and then it will be delivered to the user’s browser to load the domain. 

If there are Secondary DNS servers, they can also be set to be authoritative, and the Primary could even be hidden for extra security.

What do you need from a Primary DNS? 

The Primary DNS server must comply with certain parameters.

• It must be stable and constantly available. Propagation and DNS resolution processes can’t happen if it’s down.
• Its access must be limited for security reasons. This server must be accessible only to administrators. It holds critical information that, if wrongly manipulated, can badly threaten security and operation. 
• Reachable by most systems of the network. Especially talking about internal or small networks, sometimes they don’t have Secondary servers (redundancy). Without them, the only way to guarantee resolution is to keep the Primary DNS accessible.

Conclusion

As you see, Primary DNS servers mean a lot for networks. Their functionality allows them and your business to work as well as they do now!