Bind 9 Administrator Reference Manual

Chapter 3. Nameserver Configuration
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When a resolver queries for these records, BIND will rotate them and respond to the query with the
records in a different order. In the example above, clients will randomly receive records in the order 1, 2,
3; 2, 3, 1; and 3, 1, 2. Most clients will use the first record returned and discard the rest.
For more detail on ordering responses, check the rrset-order substatement in the options statement, see
RRset Ordering. This substatement is not supported in BIND 9, and only the ordering scheme described
above is available.
3.3. Notify
DNS Notify is a mechanism that allows master nameservers to notify their slave servers of changes to a
zone’s data. In response to a NOTIFY from a master server, the slave will check to see that its version of
the zone is the current version and, if not, initiate a transfer.
DNS Notify is fully documented in RFC 1996. See also the description of the zone option also-notify,
see Section 6.2.14.6. For more information about notify, see Section 6.2.14.1.
3.4. Nameserver Operations
3.4.1. Tools for Use With the Nameserver Daemon
There are several indispensable diagnostic, administrative and monitoring tools available to the system
administrator for controlling and debugging the nameserver daemon. We describe several in this section
3.4.1.1. Diagnostic Tools
dig
The domain information groper (dig) is a command line tool that can be used to gather information
from the Domain Name System servers. Dig has two modes: simple interactive mode for a single
query, and batch mode which executes a query for each in a list of several query lines. All query
options are accessible from the command line.
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