I have a following configuration:
Router AUX port -> FW Console
If there is something problem in the FW I can log the FW from cisco aux but the problem is now that the aux port is sending character's to FW's console port and now if the FW is rebooting it will go bootloop because when the FW boot's there is situation where is something "press any key" and now cisco router sends characters and the FW boots again.
Router AUX port config is following:
line aux 0
transport input all
Which aux-port config the Cisco won't send any character to FW's console.