This is deliberate.  There is no need for a port to be registered
for this as it is entirely private use.  rndc.conf provides a
adequate way to remember the port between invocations.

-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka@isc.org