What is the difference between normal and alternate fxp modes?

[gozu]

I'm trying to troubleshoot a computer on my lan to which I can apparently only fxp in alternate mode. I duplicated all the settings from my main computer (which has no problems), set the necessary options in the router, made it DMZ, etc.

Maybe this will bring me some insight on the nature of this puzzling problem.

Thanks for your time

Gozu