On 2011-03-15, at 16:58 , Philip Homburg wrote:
> I think the answer is that is statistically very unlikely that on a single
> subnet, a 64-bit random number will ever be equal to any address manually
> configured in DHCP.
I'd say this entirely depends on how the (usually pseudo-) random number has
been created. No RFC says it is forbidden to choose a random IPv6 address by
simply picking a number between 1-255 and pad all the bits to the left with
zeros. It may not be very advisable to do that, but it is not disallowed
either. If there was a rule like I suggested ("the first three bytes must not
be zero"), such an address would be forbidden, of course.
> Is is far more likely that by accident to ethernet cards have the same MAC
> address than that a true 64-bit random number will collide with another number
> out of a relatively small set.
See above, choosing a "very poor" random number makes this scenario very likely
and no RFC demands that "good" random numbers must be chosen, nor does any of
them define what "good" means in this context. A random number with 3 zero
bytes in a row is probably "not good", but can nonetheless be considered random.
How would two ethernet cards have the same MAC address, unless it has been
manually configured? Doesn't globally unique mean "globally unique" anymore?
Regards,
Markus
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