Re: Mac-Address uniqueness

H. Peter Anvin
2007-06-01T06:43:43Z

Avi Kivity wrote:
> H. Peter Anvin wrote:
>> Axel Kittenberger wrote:
>>
>>> Unfortunally all machines detect the same ethernet address
>>> '52:54:00:12:34:56'. Which you can guess what i means, networking comes
>>> and goes whatever machine last the ethernet address got hold of from the
>>> gateway. I tried specifing an ethernet-adress with "-net
>>> nic,macaddr=$MAC" but this also didn't work through.
>>>
>>> For now I just hardseted the mac in all machines to 52:54:00:12:34:57,
>>> 52:54:00:12:34:58 and so on.
>>>
>>>
>> This is a Qemuism. I always thought it was dumb, but I guess Qemu
>> wanted reproducibility over everything.
>>
>> IMNSHO it would have been much better to default to a random value
>> (meaning that all except the bottom 2 bits of the first octet are
>> random, those bits should be set to 10 binary.)
>>
>>
>
> That tends to consume dhcp leases quickly, if you start guests often (as
> I do). Also, some distributions use the mac address as a key for naming
> interfaces; if it changes, the guest gets confused
>

The right solution to that, of course, is a VM definitions file, so the
random Ethernet address is only generated once. For Qemu/KVM, that
could at least in theory simply be a shell script.

-hpa