[crossbow-discuss] ?: what happens on a MAC collision when creating a VNIC

[Nicolas Droux]

On Jun 23, 2009, at 5:35 AM, Steffen Weiberle wrote:

> On 06/22/09 19:14, Nicolas Droux wrote:
>> On Jun 22, 2009, at 1:51 PM, Steffen Weiberle wrote:
>>> I took a look at the docs below, and did not see how Solaris  
>>> handles a MAC collision. Since users have several options when  
>>> creating a VNIC regarding the use of or creation of a MAC address,  
>>> including specifying their own IEEE OUI, what happens if there is  
>>> a collision? Especially when it is not being set, but partially or  
>>> fully random? Does it fail, or does it re-try?
>> Steffen,
>> When a VNIC is created we have checks in place to ensure that the  
>> address doesn't conflict with another MAC address defined on top of  
>> the same underlying NIC. When the MAC address is generated  
>> randomly, and the generated MAC address conflicts with another  
>> VNIC, we currently fail the whole operation. We should try another  
>> MAC address in that case, transparently to the user, I filed CR  
>> 6853771 to track this.
>> To reduce the risk of MAC address conflicts with physical NICs on  
>> other hosts on the network, we use by default a OUI with local bit  
>> set for random MAC addresses, and we let the administrator use a  
>> different OUI or prefix if desired. We currently don't have a  
>> mechanism in place do perform automatic MAC address duplication  
>> detection between multiple hosts.
>> Nicolas.
>
> Hi Nicolas,
>
> Thanks. I did not think about internal collisions, so my question  
> was about what you addressed in the second part. I did confirm that  
> by setting a VNIC MAC address to that of another host, I can prevent  
> communications silently, and that confirms that there is no  
> duplication detection across hosts.
>
> Regarding within a system, is the check only for conflicts on the  
> same NIC, or in the whole system? I read the former, so it might be  
> possible to have multiple VNICs on different NICs with the same MAC  
> (similar to OBP local-mac-address?=false)?

Yes that's correct, it's the former, on a per NIC basis.

Nicolas.

>
> Steffen
>
> OBP=OpenBoot PROM, which has the option to use only one MAC address  
> for a system (for the times when NICs did not deliver a MAC address)  
> or to use the addresses delivered with different NICs
>
>>> Thanks
>>> Steffen
>>>
>>> http://opensolaris.org/os/project/crossbow/Docs/crossbow-drivers.pdf
>>> http://opensolaris.org/os/project/crossbow/Docs/crossbow-virt.pdf
>>> _______________________________________________
>>> crossbow-discuss mailing list
>>> crossbow-discuss at opensolaris.org
>>> http://mail.opensolaris.org/mailman/listinfo/crossbow-discuss
>
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-- 
Nicolas Droux - Solaris Kernel Networking - Sun Microsystems, Inc.
nicolas.droux at sun.com - http://blogs.sun.com/droux