+NSC also supports classless delegations for reverse zones using the mechanism
+described in RFC 2317, i.e. by putting CNAME records to the reverse zone which
+point to records of the same name in a sub-domain which you can delegate directly.
+
+For example if you want to delegate 64-127 in 0.0.10.in-addr.arpa to ns.example.net,
+you create a 64/26 sub-domain (26 is the network prefix length) and add the following
+records to 0.0.10.in-addr.arpa:
+
+ 64 CNAME 64.64/26.0.0.10.in-addr.arpa.
+ 65 CNAME 65.64/26.0.0.10.in-addr.arpa.
+ ...
+ 127 CNAME 127.64/26.0.0.10.in-addr.arpa.
+
+ 64/26 NS ns.example.net.
+
+Then you configure ns.example.net to be a primary name server for the zone
+64/26.0.0.10.in-addr.arpa and put the PTR records there:
+
+ 64 PTR sixty-four.example.net.
+ 65 PTR sixty-five.example.net.
+ ...
+ 127 PTR two-to-seven-minus-one.example.net.
+
+NSC offers special primitives for configuring such delegations, but not limited
+to the sub-domain name syntax shown above (which is recommended by the RFC, but it's
+far from being the only one used in the real world, other possibilities being for
+example 64-127, 64+64 etc.).
+
+The CNAME block can be generated by the REVBLOCK(subdomain-name, low-addr, high-addr)
+directive in the configuration of the whole reverse zone. The example above would
+be written as:
+
+ REVBLOCK(64/26, 64, 127)
+
+The sub-zone can be created automatically like any another reverse zone, you only
+need to use the three-parameter form of the REVERSE directive to specify the
+address range in order to filter out possible hosts falling outside your range.
+
+CAVEAT: The slashes in zone names are automatically translated to @'s when forming
+file names.
+
+Again for the example above, you need to put the following to cf/domains:
+
+ REVERSE(10.0.0.64/26, <list-of-domains-to-gather-the-addresses-from>)
+
+And to cf/64@26.0.0.10:
+
+ SOA(REV(10.0.0.64/26))
+ NS(<list-of-name-servers>)
+ REVERSE(10.0.0, 64, 127)
+
+NOTE: It's usually helpful to configure the primary name server for the parent
+domain (i.e., the one where you configure the delegation and create the CNAME's)
+as a secondary for the sub-zone as well, so if it replies with the CNAME, it will
+include the PTR record pointed to by the CNAME in the additional section of its
+reply, eliminating the need for an extra query.