BIND sortlist option
The sortlist option performs preferential ordering similar to topology but in ordering query results when responding to a resolver client. The sortlist option is specified with a series of address match list pairs. The first address match list of each pair is used to match the source IP address of the query to which a response is being prepared. Based on this match, the second address match list within the pair lists the preferred order of results analogously to the manner used to direct queries with topology.
sortlist {
{172.16.0/24; { 10.100.1/24; 10.100.2/24; };};
{172.16.1/24; { 10.100.4/24; 10.100.2/24; };};
};
If a query is received from the 172.16.0.0/24 address space, list returned IP addresses within the 10.100.1.0/24 network first, followed by those within the 10.100.2.0/24 network second, followed by any others in the RRset. Likewise, if a query is received from the 172.16.1.0/24 address space, list returned IP addresses within the 10.100.4.0/24 network first, followed by those within the 10.100.2.0/24 network second, followed by any others in the RRset.