What is a SOA record in DNS?

SOA record is an essential and one of the most common DNS records. It is crucial to understand it properly. So, let’s explain it!

SOA record explained.

The SOA record is the beginning of the chain of authority, which is typical for the DNS. The short SOA stands for start of authority. From all the nameservers that you have, the SOA record will show which holds the original zone file. This server will contain all of the essential data about the zone. It will be your authoritative DNS server.

Information about the zone transfer and the email of the DNS administrator of the zone, and more is inside the SOA record.

DNS is a network of name servers, and all of them need to act together. Thus SOA record is extremely important with supporting to show up-to-date data.   

A query appears at the recursive DNS server. In case it can’t resolve it with the present DNS records, the recursive server will request from the authoritative DNS server for the updated records. Afterward, it will keep them for the time established by the TTL.   

If someone makes a change within the DNS records in the authoritative name server, this data should be renewed down the chain. There is a DNS notify list. It has IP addresses of the recursive DNS servers that are allowed to access the information. So then, they can complete a transfer without the need to wait for the refreshing interval to expire. The transfer itself is possible to be a full zone transfer (AXFR zone transfer) or incremental (IXFR).

The Structure of the SOA record

The SOA record is structured with the following elements inside:

  • Name – This is simply the name of the zone.
  • Type – This is the type of DNS record. In this case, it will be SOA.
  • Primary name server – Here is the hostname of the authoritative DNS server for that specific zone.
  • Default TTL – This number is a time period. It shows for what amount of time the DNS records are valid. The secondary DNS servers must perform a zone transfer when the time runs out.
  • Refresh rate – The number here shows in seconds how often the secondary DNS server has to visit the authoritative DNS server and review for changes.
  • Retry rate – The time the secondary servers will proceed trying to update if the zone transfer fails. If the time expires before they perform the zone transfer, the secondary servers will no longer answer queries. Their data will not be up to date.
  • Admin’s email – Here, it shows the email of the administrator of the zone.
  • Serial number – The serial number of the zone which secondary DNS servers check. And also determine whether they have to update their DNS records or not.

Why is it important?

The DNS SOA record for performing zone transfer. This record contains the most recent version of the DNS records for a specific zone. It is indicating when the secondary DNS servers have to update their information.

DNS SOA record is to show the top authority about a zone. The for the zone is the authoritative name server. This record is necessary, and only one should exist in a zone. If for some reason, you insert more than one SOA record, your zone will not function.

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