[ kvm-Bugs-1858946 ] Qemu doesn't warns user about incorrect MAC Address

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Bugs item #1858946, was opened at 2007-12-27 09:20
Message generated for change (Comment added) made by aliguori
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Category: None
Group: None
Status: Open
>Resolution: Invalid
Priority: 5
Private: No
Submitted By: Technologov (technologov)
>Assigned to: Anthony Liguori (aliguori)
Summary: Qemu doesn't warns user about incorrect MAC Address

Initial Comment:
NOTE: This is a qemu problem/lack-of-feature, not a KVM one.

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.

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>Comment By: Anthony Liguori (aliguori)
Date: 2008-05-26 13:14

Message:
Logged In: YES 
user_id=120449
Originator: NO

No MAC address is valid unless you have been assigned it.  It's the user's
responsibility to ensure that the MAC addresses they are using are valid
and won't cause conflicts on their network.

Blacklisting a certain group of MAC addresses doesn't make the problem
much better because people can still end up using "random" MAC addresses
which are actually valid on their network.  We need to encourage people not
to use "random" MAC addresses, it's always wrong.

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You can respond by visiting: 
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