name {ttl} addr-class SOA Origin Person in charge
@ IN SOA ucbvax.Berkeley.Edu. kjd.ucbvax.Berkeley.Edu. (
1995122103 ; Serial
10800 ; Refresh
1800 ; Retry
3600000 ; Expire
259200 ) ; Minimum
The Start of Authority, SOA, record designates the start of a zone. The name is the name of the zone and is often given as ``@'' since this is always the current $ORIGIN and the SOA RR is usually the first record of the primary zone file.
Origin is the name of the host on which this data file resides (in other words, the primary master server for this zone.) Person in charge is the e-mail address for the person responsible for the name server, with ``@'' changed to a ``.''.
The serial number is the version number of this data file and must be a positive integer. This number must be incremented whenever a change is made to the data. Older servers permitted the use of a phantom ``.'' in this and other numbers in a zone file; the meaning of n.m was ``n000m'' rather than the more intuitive ``n*1000+m'' (such that 1.234 translated to 1000234 rather than to 1234). This feature has been deprecated due to its obscurity, unpredictability, and lack of necessity. Note that using a ``YYYYMMDDNN'' notation you can still make 100 changes per day until the year 4294. You should choose a notation that works for you. If you're a clever perl programmer you could even use RCS version numbers to help generate your zone serial numbers.
The refresh indicates how often, in seconds, the secondary name servers are to check with the primary name server to see if an update is needed.
The retry indicates how long, in seconds, a secondary server should wait before retrying a failed zone transfer.
Expire is the upper limit, in seconds, that a secondary name server is to use the data before it expires for lack of getting a refresh.
Minimum is the default number of seconds to be used for the Time To Live field on resource records which do not specify one in the zone file. It is also an enforced minimum on Time To Live if it is specified on some resource record (RR) in the zone. There must be exactly one SOA record per zone.