Description

Starting RIOT on the nucleo-f767z1 Ethernet sometimes fails to work often after flashing a new firmware sometimes after a reset most the time the green Ethernet-connector-LED stays dark when this happens.

Steps to reproduce the issue

make and flash a IPv6 example to the nucleo-f767z1 and run a PING to its IPv6 address keep the ping running (linux does it endlessly by default)

do resets (button) short and long presses
do reflashes

Expected results

ping works every time after RIOT boot (real network issues aside)

Actual results

ping does not work after some resets or flashes

Versions

current master