Many Kerberos 4 sites also run the Andrew File System (AFS).
Modern AFS servers (OpenAFS > 1.2.8) support the AFS 2b token format.
This allows AFS to use Kerberos 5 tickets rather than version 4
tickets, enabling cross-realm authentication. By default, the
krb524d service will issue the new AFS 2b tokens. If you are
using old AFS servers, you will need to disable these new tokens.
Please see the documentation of the appdefaults section of
krb5.conf in the Kerberos Administration guide.