Bind 9 Administrator Reference Manual

Chapter 6. BIND 9 Configuration Reference
6.2.14.12. RRset Ordering
When multiple records are returned in an answer it may be useful to configure the order of the records
placed into the response. The rrset-order statement permits configuration of the ordering of the records
in a multiple record response. See also the sortlist statement, Section 6.2.14.11.
An order_spec is defined as follows:
[ class class_name ][ type type_name ][ name "domain_name"]
order ordering
If no class is specified, the default is ANY. If no type is specified, the default is ANY. If no name is
specified, the default is "*".
The legal values for ordering are:
fixed Records are returned in the order they are defined in the zone
file.
random Records are returned in some random order.
cyclic Records are returned in a round-robin order.
For example:
rrset-order {
class IN type A name "host.example.com" order random;
order cyclic;
};
will cause any responses for type A records in class IN that have "host.example.com" as a suffix, to
always be returned in random order. All other records are returned in cyclic order.
If multiple rrset-order statements appear, they are not combined — the last one applies.
Note: The rrset-order statement is not yet implemented in BIND 9. BIND 9 currently supports only a
"random-cyclic" ordering, where the server randomly chooses a starting point within the RRset and
returns the records in order starting at that point, wrapping around the end of the RRset if necessary.
6.2.14.13. Synthetic IPv6 responses
Many existing stub resolvers support IPv6 DNS lookups as defined in RFC1886, using AAAA records
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