Fail Open feature on the WAN connections

[Ahmad_Murad]

Hi, I' m new to the FortiFate appliances, and I have FG600C device, and need to deploy it as additional security layer before 3rd party firewall. The topology will be like the following: ISP --- Router --- 1st FW --- FG600C --- Core SW I read about the device and see that the WAN interface is FAIL OPEN (2 Interfaces for WAN1, and the same for WAN2). I tried to search for Solid answer about the FAIL OPEN but I cannot find, so anyone has a clear answer about it? Also, what I think that I can use any Ethernet interface/ports to connect the Internal and External interfaces to the network, right?