To upgrade from OpenLDAP 2.2 to OpenLDAP 2.3 on CentOS 4.3, you need to update yum, the automatic updater/package installer/remover for RPM systems. Then you’re ready to upgrade your OpenLDAP packages. First, point yum at the CentOS development repository, or repo, by adding these lines to /etc/yum.repos.d/CentOS-Base.repo:

\[testing\]
name=CentOS-$releasever - Testing
baseurl=http://dev.centos.org/centos/

$releasever/testing/$basearch/
enabled=1
gpgcheck=1
gpgkey=http://dev.centos.org/centos/

RPM-GPG-KEY-CentOS-testing

Next, upgrade your OpenLDAP packages using this command:

# yum -y install openldap.i386 openl
dap-clients.i386 openldap-devel.i386
  openldap-servers.i386

Upgrading may take a while, as yum needs to update all packages related to OpenLDAP as well.