[Qemu-devel] Qemu doesn't warns user about incorrect MAC Address

[Alexey Eremenko]

I Tried to launch 2 VMs connected back-to-back on the same host, but nothing worked, so I wasted a lot of time figuring it out, and my time could be saved, if Qemu could give proper warning on user stupidity/incorrect action.

At the end, my colleague pointed me to this problem.

Actually I used MAC addresses, that begin with "01:xx:xx:xx:xx:xx" which are multicast MAC addresses, and are illegal to assign them to NIC, and neither the guest OS (Windows XP), and not Qemu didn't complain about that, but the network simply didn't work. The NIC (RTL8139) was detected and installed by the guest OS, without a problem.

The full list of illegal MAC addresses, that are Multicast/Broadcast is listen below:
http://www.cavebear.com/archive/cavebear/Ethernet/multicast.html

Correct behavior would be: to warn a user of his incorrect action, but continue running a VM.
Now I just wasted 6 hours.

Please improve Qemu to save other people's time...

-Alexey Technologov, 26.Dec.2007.