public void setAlternateBaseDN(LdapName alternateBaseDN) {
        this.alternateBaseDN = alternateBaseDN;
        if (alternateBaseDN == null) {
            properties.remove("ldap.alternateBaseDN");
        }
        else {
            properties.put("ldap.alternateBaseDN", alternateBaseDN.toString());
        }
    }
Sets the alternate starting DN that searches for users will performed with.
Searches will performed on the entire sub-tree under the alternate base DN after
they are performed on the main base dn.

@param alternateBaseDN the alternate starting DN used for performing searches.
xmppserver/src/main/java/org/jivesoftware/openfire/ldap/LdapManager.java