On Dec 20, 2012, at 12:54 AM, Rémi Després wrote:
> Interface addresses at the link layer are specified by IEEE to be universally
> unique.
Yes, and EIU-64 is one of several seeds from which an IID can be derived. It's
not the only one. The fact that an underlying technology provides an
intended-to-be-globally-unique value (not that it actually *is* globally
unique, but it is intended to be) is a happy accident, but not a requirement
for the value we derive from it.
To make assertions about IP addresses based on the EUI-64 is to impose
requirements that don't actually exist in IP. It's a little like saying that
concrete MUST ("are required to") be grey because the rocks we use in it happen
to be grey; no I can have concrete of other colors if I want.
The comment Brian is making refers to IP's requirements, which are that the IID
used in a subnet by an interface must be unique within that subnet. If one has
a physical machine with an interface that supports a dozen virtual machines,
the requirement is not that all of the physical and virtual machines use IP
addresses derived from the physical interface MAC address; the requirement is
that they each have IIDs that are unique within the subnet. The obvious choice
will be to use privacy addresses for the VMs, which will appear outside the
physical machine as the one interface having that many IP addresses.
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