[ovirt-users] Guest PXE boot with 2 NICs : MAC order

[Lior Vernia]

On 31/03/15 16:02, Nicolas Ecarnot wrote:
> Le 31/03/2015 14:48, Lior Vernia a écrit :
> 
>>>> I see. It seems MAC addresses are allocated according to the NIC name
>>>> order,
>>>
>>> I'm not sure this is exact.
>>> According to what I'm witnessing, MAC addresses are allocated in
>>> incremental order, from the first free MAC address in the MAC pool
>>> range.
>>>
>>
>> My question is as follows: when you create a VM, and add NICs as part of
>> the new VM dialog (using the widget at the bottom), have you ever
>> encountered a situation where a "higher-named" NIC got a lower MAC
>> address?
> 
> Absolutely YES.
> I just repeated this test, and it is easy to reproduce : in a MAC pool,
> manage to free some lower MAC addresses, and the will get allocated from
> the first free in the pool.
> 

So the lower ones are allocated. But I would expect nic0 to receive a
lower MAC address than nic1 on the same VM. Have you encountered a
situation where that is not the case?

> And I found this behaviour SOUND. Don't change it.
> 
>>>> So the only problem here is how gPXE chooses a NIC to boot
>>>> from... I'm not familiar with the behavior of gPXE, but oVirt seems to
>>>> behave alright.
>>>
>>> I mostly agree with that, in the sense that one has to dig in which way
>>> gPXE is sorting the NICs, ie mapping the MACs to its "net0", "net1", and
>>> so on.
>>>
>>
>> That's the key point here for me, as it's difficult to predict the
>> behavior of n'importe quel piece of software... :)
> 
> Thanks for your explanation, though I think the present way oVirt is
> assigning the MACs and naming the interfaces are not bad and should not
> change.
> The key point is how to make oVirt force gPXE to use the interface we
> want, whatever its name or its MAC. If possible?
> 
> It seems I'm not the first one to deal with this issue :
> http://etherboot.org/pipermail/gpxe/2011-September/001742.html
>