Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/STMicroelectronics/STM32F107xx/ETHERNET_MAC/MACA3HR#0x0
Ethernet MAC address 3 high register (ETH_MACA3HR)
MAC address3 high
Mask byte control
Source address
Address enable
https://github.com/cmsis-svd/cmsis-svd-data