I have Intrushield 3000 appliance.I have also fail open kit.How to configure IPS with fail open kit (physical cable connection with IPS-fail open kit and system configuration in Intrushield 3000 for fail open.
Please take a look on the KB60811 - https://kc.mcafee.com/corporate/index?page=content&id=KB60811&actp=search&viewlocale=en_US&searchid=... which might help you.
Besides the KB that Bruno refers, I will tell you my personal experience with FOK:
1) If you are working with Gigabit speeds please read attached KB, Gigabit and Fail Open Considerations item.
2) In FOK there is a white LED that indicates comunication between sensor and FOK. That LED won´t turn on until you put ports in "Enable".