Hello Yelin,
The ITS system is for filing bug reports, not for asking help with slapd configuration. The correct resource for configuration questions is the openldap-technical list:
http://www.openldap.org/lists/mm/listinfo/openldap-technical
Your understanding of how this feature works is incorrect. As noted in the slapd.conf(5) man page:
bind_anon_cred allows anonymous bind when credentials are not empty (e.g. when DN is empty).
The option you are looking for in your case is:
bind_anon_dn allows unauthenticated (anonymous) bind when DN is not empty.
This ITS will be closed.
Regards, Quanah
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Quanah Gibson-Mount Product Architect Symas Corporation Packaged, certified, and supported LDAP solutions powered by OpenLDAP: http://www.symas.com