Two things I notice from below: olcTLSCACertificateFile: /etc/openldap/certs/ca_cert.pem -rw-r--r--. 1 root root 1696 Sep 22 14:18 ca-cert.pem Underscore in the first, dash in the second.
Good catch!It's also important to note that RedHat links to MozNSS rather than GnuTLS or OpenSSL, so the standard caveats apply, and be sure to follow the documentation to MozNSS when setting up both the slapd and client (ldapsearch) side of things.
--Quanah -- Quanah Gibson-Mount Product Architect Symas Corporation Packaged, certified, and supported LDAP solutions powered by OpenLDAP: <http://www.symas.com>