It is not important whether these nameservers are slaves or if one is a master; they are both still considered authoritative. This refers to the PoinTeR record, which is designed to point to another part of the namespace. PTR records are primarily used for reverse name resolution, as they point IP addresses back to a particular name. Refer to Section This refers to the Start Of Authority resource record, which proclaims important authoritative information about a namespace to the nameserver.
Located after the directives, an SOA resource record is the first resource record in a zone file. The following shows the basic structure of an SOA resource record:. When configuring BIND, all times are specified in seconds. However, it is possible to use abbreviations when specifying units of time other than seconds, such as minutes M , hours H , days D , and weeks W. The table in Table The following example illustrates the form an SOA resource record might take when it is populated with real values.
Seen individually, directives and resource records can be difficult to grasp. However, when placed together in a single file, they become easier to understand. In this example, standard directives and SOA values are used. The authoritative nameservers are set as dns1. Since the server1 and server2 names do not end in a trailing period. Through the related A resource records, their IP addresses can be determined. FTP and Web services, available at the standard ftp. This zone file would be called into service with a zone statement in the named.
It looks very similar to a standard zone file, except that PTR resource records are used to link the IP addresses to a fully qualified domain name. Any host labels below the origin will append the origin hostname to assemble a fully qualified hostname.
Any host label within a record that uses a fully qualified domain terminating with an ending period will not append the origin hostname. This is typically used for the apex of a zone. An SOA record is required for each zone. A zone file is a collection of resource records with each record entry described in the following sequence:. Follow these instructions to update the zone file.
This is an example of a zone file exported from GoDaddy. This recipe describes the basic zone file format without any resource records suitable for any type of zone file. There is no requirement for filenames with zone file, but a reasonable standard is db.
The longer this period, the longer it will take to propagate changes to the zone files. The shorter the TTL, the harder your DNS servers will work beacuse non-authoritative servers will have to ask it the same question more frequently. Values from a few hours to a day are reasonable. An integer TTL value is interpreted as seconds, although for those of us who are not walking calculators, adding m at the end means minutes, h hours, d days, and w weeks.
A day would be represented by any of the following lines:. The SOA section is an intimidating chunk of code for the uninitiated, but each field in the SOA has a meaningful purpose. Taken a piece at a time, it is simple. Serial number This value is perhaps the greatest source of DNS-related head scratching. To make things fast and efficient, BIND processes zone files into another format.
When BIND loads a zone file at startup, it checks the serial number and only processes the zone file if the serial number is bigger than its previously processed version.
So, if you change the zone file but not the serial number, BIND will ignore the changes.
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