I really want to clone an "illegal" multicast eth0 MAC address (forbidden numbers) on Ubuntu 16.04 Xenial in order to use a legal (and paid for) development license for design package X. I've gone through all the obvious ways of spoofing (ifconfig up, down, macchanger here, network manager there...) and have had great success with unicast addresses, but I'm stuck now...any suggestions on how to circumvent/force the Ubuntu kernel ?

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    What tool are you using. What number are you trying to assign. Do you mean you're trying to give your eth0 an unassignable multicast address (as in the linked question)? – pbhj Nov 10 '16 at 23:44
  • I want to change eth0 HWaddr (using e.g. IFCONFIG ). If it's a unicast MAC, Ubuntu allows it. If it's multicast, Ubuntu rejects the change. – ianx Nov 11 '16 at 9:57
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    @pbhj ...and I do not intend to actually use eth0 after it's MAC has been cloned. I just need it set to a very specific MAC address (coincidently a multicast address) such that my apllication's license manager can read the HWaddr field and activate said license. – ianx Nov 11 '16 at 15:36
  • From my research it's down to the driver, so some devices will allow you to set an address that doesn't work; ifconfig asks the driver to set the address though. I tried with VirtualBox and it too prevents multicast HWADDR from being set. – pbhj Nov 18 '16 at 16:44
  • @pbhj It seems that I'm pretty screwed here...Well, thank you for your time spent. I have learned in the process. – ianx Dec 4 '16 at 16:11

You could always recompile a patched kernel without that limitation, but I recommend you to take a step back and determine how does package X obtain the MAC address.

You don't really need to forge the MAC address, just the output of whatever is the package using to obtain it (eg. providing a fake ifconfig).

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