That eeprom field wasn't used on the v2.3/v2.4 boards. When the v2.5 boards are manufactured the field is programmed as is the board serial number. Serial number is used to derive and program the static MAC address in the eeprom. This process is not performed when the v2.3/v2.5 board's BMC firmware is upgraded to v2.1.0. Sven posted the process here (somewhere) to write-enable the eeprom and update the appropriate fields. You can also rip the "factory" boot image apart to figure out the process. It's doable, but entirely undocumented. I borked a v2.4 board's ability to boot the first time I tried it. Thankfully, it was recoverable, but that process is also undocumented.