If yum updates or yum anything provides a network error or if you simply want to unregister the system from a managed server like RHN Classic, Red Hat Satellite, Katello, or Spacewalk, there is a only one file in the way.
If presented with an error similar to this:
yum repolist Loaded plugins: fastestmirror, refresh-packagekit, rhnplugin, security Network error: unknown protocol This is likely the result of a system that is connected to Spacewalk or some other RHN-Register that is not available.
To resolve delete one file.
rm -f /etc/sysconfig/rhn/systemid