Re: Software to test MAC address privacy

[Robert Moskowitz <rgm htt-consult com>]

On 08/03/2014 04:58 AM, Glen Turner wrote:
> On 19/07/2014 Robert Moskowitz wrote:
> > Actually the standard uses the first 2 bits for this. It is called local scope MAC addresses. This leaves 46 
> > bits for the random content. Thus if you have a network of 10000 devices the probablity of a collision is 
> > 7x10^-7
> Hello Robert,
>
> Not all locally-assigned addresses are available for use as random MAC addresses. Last I looked that are 
> historical uses of LAS for DECnet and other protocols from 00:… through to 05:…. It would be useful if the 
> IEEE recommended a range of LAS for host use (ie, virtual machine MAC addresses) and specified a range for 
> your random MAC address proposal. Such a range should leave sufficient LAS for other potential future 
> applications.

This is actually in progress.  We are forming a study group in IEEE 802 
(first session will be at the November San Antonio meeting) to fully 
document this and come out with a recommended practice.  One of the 
other drivers is the cloud computing world.  There is talk about 
partitioning the use of the LAS.  I am against that as it increases the 
collision probablity.  Perhaps by usage domain.

In any case we will have to work out probe/discovery methods to discover 
collisions for readdressing.

thanks for your input.  I will see it gets included in the discussion.