Hello,
I don't have any documentation on detailed steps to set it up.
By default eth0 of the Control appliance should have DHCP/Kerberos snooping enabled. The requirement would be that the network mirror all kerberos (port 88) traffic into the NAC's eth0, or you can split out and use eth1 for DHCP/Kerberos snooping as well.
From the perspective of control the Kerberos snooping configuration is already enabled by default.
It depends on how the Control appliance is situated in your network and if it would be possible to mirror a centralized link that has all Kerberos traffic.
Thanks
-Ryan