Hi,
If you are looking into having Liferay authenticate users from an existing LDAP-server (=Liferay acting as a LDAP client) then you do not have to install anything extra.
Liferay can be configured to integrate users from LDAP like this
Documentation on LDAP authentication , And there are multiple topics on the forum about this aswell. And yes, it goes from Control Panel - Portal Settings - Authentication..
If you are however looking to have Liferay act as a LDAP server on it's own, then there is a plugin in the Enterprise Edition Marketplace called Virtual LDAP Server EE, which can be used to achive that. The documentation regarding that is not very thorough, but please let me know if you need help on it. I've set it up a few times.
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