I had at first tried to pre-stage the computer's account in Active Directory, but when my first adjoin attempt failed, I deleted that account so it would join into the default Computers container (not an OU). Result of adjoin was unfortunately the same.
Is there any reason this might succeed on CentOS 7 but not on CentOS 6? Last week I successfully joined a CentOS 7 box using this same method (with no complaining about Kerberos FAST) but this week this isn't working on CentOS 6. It's possible, but not likely, that Kerberos FAST was enabled in the past few days; I will ask the other admins about it.
Is there any reason this might succeed on CentOS 7 but not on CentOS 6? Last week I successfully joined a CentOS 7 box using this same method (with no complaining about Kerberos FAST) but this week this isn't working on CentOS 6. It's possible, but not likely, that Kerberos FAST was enabled in the past few days; I will ask the other admins about it.