Hi

it seems it was following an update.

It doesn't bother me in fact the new one had already been used probably with another distribution.

But I wonder where are they stored ?

or how are they guessed

before : E6:7C:8E:9F:AC:D0

now     : 7E:C3:14:57:E7:B1

MAC address is generated based on SID in U-Boot. This is something like eFuse and calibration register. It should be unique number, but because of HW bug it was not (mostly zeros) if you directly read it first time. Latest U-Boot has fix for that, you can refer to #linux-sunxi log and mailing list if you want technical details. Of course, this fix influenced MAC address.

OK no problem .

In fact as the new MAC address was already in my DHCP it means that at least another distribution

uses the same way to choose it.