LDAPS Server 2012 R2 Error 0

Good morning,

We're trying to get information from our DC via LDAPS and have hit a wall, so we are reaching out for some help from all you lovely people!

When trying to connect, we keep getting Error 0 messages (we are using ldp.exe to test connection):

ld = ldap_sslinit("dc1.domain.local", 636, 1);
Error 0 = ldap_set_option(hLdap, LDAP_OPT_PROTOCOL_VERSION, 3);
Error 0 = ldap_connect(hLdap, NULL);
Error 0 = ldap_get_option(hLdap,LDAP_OPT_SSL,(void*)&lv);
Host supports SSL, SSL cipher strength = 256 bits
Established connection to dc1.domain.local.
Retrieving base DSA information...
Getting 1 entries:
Dn: (RootDSE)
<blarb from here removed>
-----------

We've been through THIS process to create an SSL and Root Certificate and installed them on the server and that does not seem to have made any difference.

We have also checked that there is no certificate in the Service, Active Directory Domain Services Personal Store (as there have been references that we have come across where people simply had to remove a certificate from there to get things working); there is no certificate there.

We have tried creating the UseHostnameAsAlias registry key (HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ldap) and set it to 1, but that only seems to cause another error (if you connect by server name; the error above is what you get if you try to connect by FQDN):

ld = ldap_sslinit("dc1", 636, 1);
Error 0 = ldap_set_option(hLdap, LDAP_OPT_PROTOCOL_VERSION, 3);
Error 81 = ldap_connect(hLdap, NULL);
Server error: <empty>
Error <0x51>: Fail to connect to dc1.

Our Primary DC is a Server 2008 R2 box, we have a secondary that's 2012 R2 and a further 3 at remote sites and 2 in Azure (don't know if this would make any difference at all, but thought it worth mentioning).

Any help on this would be greatly appreciated.


Kind regards,
Kyle