188.8.131.52 - Unauthenticated Authentication
The Unauthenticated Authentication mechanism is a bit specific. First of all, none all the LDAP servers support such a mechanism. In fact, the default behavior is for server to return a unwillingToPerform result code when someone tries to bind using a null password.
We won't go any deeper into this 'feature', those interested in the rational behind it and the associated drawbacks can read the following links :