Why do I see the error 'rndc: connection to remote host closed' when I try to start named?

One possible cause for this error is an incorrectly referenced rndc key. The rndc symmetric encryption key is contained in the /etc/rndc.key. This file is included into the /etc/named.conf bind nameserver and /etc/rndc.conf rndc utility configuration files. Bind and rndc use the rndc key to encrypt their communications.

By default, named.conf...