Will it damage the NX to have some brief Ethernet signals present on the pins BEFORE power up?
The Design Guide states
The carrier board cannot drive high or pull high any signals that are associated with the
module when the module rails are off. If the designer cannot guarantee a signal will not be
driven or pulled high, then either the power rail related to that signal should be left off, or the
signals would need to be buffered to isolate them from the module pins. The buffers should only
be enabled towards the module when SYS_RESET* goes high.
I have buffered all the other signals to the NX on my custom carrier board, with the exception of Ethernet (which is connected to pins GBE_MDI0_P and _N, and GBE_MDI1_P and _N.)