BIND configures a number of “empty zones” to prevent recursive servers from sending unnecessary queries to Internet servers that cannot handle them (thus creating delays and SERVFAIL responses to clients who query for them). These empty zones ensure that immediate and authoritative NXDOMAIN responses are returned instead. The configuration option empty-zones-enable controls whether or not empty zones are created, whilst the option disable-empty-zone can be used in addition to disable one or more empty zones from the list of default prefixes that would be used.

The number of empty zones created for RFC 1918 prefixes has been increased, and users of BIND 9.9 and above will see the RFC 1918 empty zones both when empty-zones-enable is unspecified (defaults to yes), and when it is explicitly set to yes.