Configure X3 for ldap authentication

You must have I think libldap2-dev installed (via apt), and then ./configure should find ldap libs and tell you so at the end. config.log should give a clue, if it has WITH_LDAP set.

Find the LDAP section of x3.conf, and setup your settings...

        "ldap_enable" "1";
        "ldap_uri" "ldap://localhost";
        "ldap_base" "ou=Users,dc=afternet,dc=org";
        "ldap_dn_fmt" "uid=%s,ou=Users,dc=afternet,dc=org";
        "ldap_autocreate" "1"; // automatically create accounts if they exist in ldap but not x3
        // If you will be allowing users to register on IRC you need these:
        "ldap_admin_dn" "cn=admin,dc=afternet,dc=org";
        "ldap_admin_pass" "******";
        "ldap_object_classes" ( "top", "inetOrgAnonAccount" );
        //      NOTE: inetOrgAnon is something I made up. its schema
        //      can be found in the tools/ directory. ldap servers wont
        //      know what that is by default.
        // These configure what I store, and where.
        "ldap_field_account" "uid";
        "ldap_field_password" "userPassword";
        "ldap_field_email" "mail";
        // This bit is needed if you want to put ircops into a group. 
        // You have to create the groups ou first in something like phpLdapAdmin:
        "ldap_oper_group_dn" "cn=Opers,ou=Groups,dc=afternet,dc=org";
        "ldap_oper_group_level" "499"; // must be above this level to be added to oper ldap group
        "ldap_field_group_member" "memberUid"; // what field group members are in

Then, I suggest running x3 in foreground debug mode, and try things out a bit.