FreeRADIUS has support for LDAP, which is enabled by installing the
Using LDAP requires the use of a low-privileged user with permissions to search the directory and retrieve attributes from it, if necessary.
Using the LDAP protocol itself
Because LDAP is a directory access protocol, FreeRADIUS support relies on the directory it connects to to provide the password in a format it understands. The LDAP module will use a defined user to connect to the directory and search for the specified username, before it retrieves the appropriate password attribute.
The password can be in different formats, but the administrator implementing the FreeRADIUS connection to the directory must specify in the LDAP configuration which password attribute will be required. For more information, see http://wiki.freeradius.org/modules/Rlm_ldap.
Using the LDAP "bind as user" method
FreeRADIUS also supports the so-called bind-as-user method of authentication, in which FreeRADIUS attempts to use the username and password provided to connect to the directory. If the bind with the provided combination is successful, FreeRADIUS considers this a successful authentication attempt. For more information on this method, please read http://deployingradius.com/documents/protocols/oracles.html
For directories that defer authentication to another mechanism, such as Kerberos or SASL, or for those unable to install SAMBA to enable access to Active Directory, this method is recommended.