I've been testing the cloned MAC address feature of Network Manager on a wireless connection and found out something odd: some particular addresses, such as 00:00:00:00:00:00 and 11:11:11:11:11:11, won't work and the MAC address will default to the permanent one.
Thought this might have something to do with the addresses being unrealistic, but addresses like 22:22:22:22:22:22 or aa:aa:aa:aa:aa:aa work perfectly fine, despite not being associated with any known vendor (according to macchanger -l
and macvendorlookup.com).
Is this a bug or is there any particular reason for some MAC addresses not to be accepted?
The command I'm using to change MAC address is
nmcli connection modify [connection name] 802-11-wireless.cloned-mac-address [desired mac address]
To apply the change, I do
nmcli connection down [connection name]
nmcli connection up [connection name]
then, to verify the MAC address has changed,
macchanger -s [interface name]
I get the same behavior when I do all this via GUI and on a wired connection.
Best Answer
I enquired with GNOME Bugzilla. Here’s their informative response:
the second part meaning that all MAC addresses in the following forms are multicast and therefore unassignable:
The Wikipedia page on multicast addresses also mentions this.