What is a possible cause for this permission issue?

An Isilon administrator is receiving “permission denied” while accessing a file on a cluster that an end-user created through an SMB share. The end-user is unable to access the share from their UNIX server.

The end-user “mydomain.comwin_user1” as the login name to access the Microsoft Windows share and then used an LDAP account name of “ux_user1” to access the UNIX mount. The Isilon cluster is joined to the “mydomain.com” Active Directory domain. In additional, the cluster has an LDAP provider attached to it while the on-disk identity is set as “Native”.

What is a possible cause for this permission issue?
A . Usermapping rule is not present.
B . RFC2307 is not configured on the Active Directory.
C . On-disk identity is set as “Native”.
D . Fake UID generation in the cluster is disabled.

Answer: B