Quoting "Boyack, Kurt" :

> Rrset-order was introduced in 8.2 and dropped with 9.1, but it is not =
> needed to do round-robin; it is used to turn round-robin off.

Here is the exact quote from the Bind 9.3 documentation. 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

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:

Records are returned in the order they are defined in the zone file.

Records are returned in some random order.

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

Note: The rrset-order statement is not yet fully implemented in BIND 9. BIND 9
currently does not support "fixed" ordering.