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

[Nicolas Ecarnot]

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.

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

-- 
Nicolas Ecarnot