I am having a similar issue.. We are trying to get Lion Server to authenticate to an Active Directory server, but we can't use the Active Directory plugin, because the computer is going to sit in our DMZ. We are trying to have Lion Server look at our AD servers using the LDAPv3 plugin, but I don't know what mappings and attributes to use to have it authenticate. We started playing around with it, and we can see users in AD, but we can't import them into Lion Server or login to the Lion server. It just acts like it can't find the user accounts. We did a packet capture, and we can see that it is querying the AD server and its returning results, but the Lion Server app is not displaying them.
Thanks Sam! With the modification described in the link you provided, along with the modification found in a reply there (http://www.fh-trier.de/index.php?id=12207), we were able to get our Lion clients authenticating against OpenLDAP.
Here are the authors:
Ralf Becker: http://www.fh-trier.de/index.php?id=12207