In Server Admin, if you click the Join Kerberos button immediately after configuring Directory Access to bind to a directory system (such as Active Directory), the Join Kerberos dialog may appear blank or contain incorrect prompts, such as a request for Kerberos realm or DNS server.
Some of the required network information takes a moment to populate after binding to a directory system, so you can avoid the issue by simply waiting 30 to 60 seconds before clicking the Join Kerberos button.