Networking Guide
Chapter 6, Configuring the Domain Name Service

SOA (start of authority) resource record

SOA (start of authority) resource record

The SOA record designates the start of a zone and must appear at the beginning of every DNS hosts file. An SOA record includes the following fields:

``Name''
Name of the zone.

``Origin''
Name of the host on which this data file resides.

``Person in charge''
Mailing address for the person responsible for the name server.

``Serial number''
Version number of this data file; this number should be incremented whenever a change is made to the data. The use of a decimal point in the serial number is not recommended.

``Refresh''
How often, in seconds, a secondary name server is to check with the primary name server to see if an update is needed.

``Retry''
How long, in seconds, a secondary server should wait before retrying a failed zone transfer.

``Expire''
Upper time limit, in seconds, that a secondary name server is to use the data before it expires for lack of getting a refresh.

``Minimum''
Default number of seconds to be used for the time-to-live field on resource records that do not specify one in the zone file.
There should only be one SOA record per zone. 


Here is an example of an SOA record:

   name {ttl} addr-class SOA     Origin                Person in charge
   @          IN         SOA     volga.mynet.COM.      dave.mynet.COM (
                         1993041403     ; Serial
                         3600           ; Refresh
                         300            ; Retry
                         3600000        ; Expire
                         259200)        ; Minimum