From Netscape LDAP SDK for C LDAP SDK for C document

- http://docs.iplanet.com/docs/manuals/dirsdk/csdk41/html/contents.htm

Specifying the LDAP Version of Your Client

If you plan to call API functions that make use of LDAPv3 features, you should set the protocol version of your client to LDAPv3. (By default, clients built with the Netscape LDAP SDK for C identify themselves to LDAP servers as LDAPv2 clients.)

To specify the LDAP version supported by your client, call the ldap_set_option() function and set the LDAP_OPT_PROTOCOL_VERSION option to the value 3. For example:

...

version = LDAP_VERSION3;

ldap_set_option( ld, LDAP_OPT_PROTOCOL_VERSION, &version );

위에 적혀있는 URL을 프로그래밍할때 참고 하시면 도움이 되겠네요