I have noticed that the Stm32F767 Nucleo does not always start Ethernet reliably. For testing I used one of the example on the STM32Cube_FW_F7_V1.4.0 for the STM32F746ZG-Nucleo base of LWIP.
I set up a DOS windows to ping the board, and from every 10 resets or power ups of the board, about half of them fail to respond to the pings.
I am evaluating the Stm32F767 and Lan8720A and I am a bit disappointed at this reliability issue.
I also wrote a small program using Keil Rtos and also have the same problem.
The link leds are both on and the activity led blinks but no ping response.
Looking at the Ethernet MMC register just the receive crc error register increments.
Any ideas on how to debug this?