Comment 16 for bug 153727

Revision history for this message
Andreas Troschka (signupbox) wrote : Re: Ethernet device's number increases by one after every reboot

NICs have correct MAC address stored at production time. Therefore some applications like macchanger (Linux) and some MoBo' BIOSes enable the user to change without any correctness check the MAC address.

To create a workaround to this, in the Linux kernel an attendibility check is performed in drivers/net/forcedeth.c, where a bug seems to be present.
If the LSB red is 1, the address is considered as a multicast type (read IANA specs) and evaluated as wrong.
In this case the code calls a random MAC address generator routine and the result is stored in the NIC.

The bug consists in the fact the MAC address is red with inverted byte order so every last digit higher then 7h will trigger the multicast type case during attendibility check.

Regards