SOA record


A Start of Authority record is a type of resource record in the Domain Name System containing administrative information about the zone, especially regarding zone transfers. The SOA record format is specified in RFC 1035.

Background

Normally DNS name servers are set up in clusters. The database within each cluster is synchronized through zone transfers. The SOA record for a zone contains data to control the zone transfer. This is the serial number and different timespans.
It also contains the email address of the responsible person for this zone, as well as the name of the primary master name server.
Usually the SOA record is located at the top of the zone. A zone without a SOA record does not conform to the standard required by RFC 1035.

Structure

; name
; IN
; SOA
; MNAME
; RNAME
; SERIAL
; REFRESH
; RETRY
; EXPIRE
; TTL, a.k.a. MINIMUM

Sample SOA record in [BIND] syntax


$TTL 86400
@ IN SOA startech60serve root.startech60serve.com. (
 2018110201 ;Serial
 3600 ;Refresh
 1800 ;Retry
 604800 ;Expire
 1800 ;Minimum TTL
 IN NS startech60serve
 IN A 192.168.1.3
 IN MX 10 startech60serve
startech60serve IN A 192.168.1.3

Serial number changes

Several methods have been established for updates to the SERIAL field of a zone's SOA record: