Welcome to the CentOS fora. Please see the recommended reading for new users linked in my signature.
Not sure what you're looking at as there is no CentOS-6 documentation set. A google on "active directory" "enterprise linux 6" site:redhat.com
turns up Chapter 10 in the upstream Deployment Guide
. Does that help? If not, please read all
the links in my signature and try again. About all you have told us so far is that it does not work.