+FORWARDED(zone, ip...)
+ Define a forwarding zone. All queries are forwarded to the
+ specified name servers.
+
+BLACKHOLE(zone)
+ Define an empty zone according to RFC 6303. This is usually done
+ for zones for which clients are known to erroneously ask queries
+ (e.g., reverse resolving of link-local addresses). The contents
+ served for these zones is taken from cf/blackhole.
+