How are you doing DHCPv6 ?

Karl Auer kauer at
Mon Jan 23 22:56:58 UTC 2012

On Mon, 2012-01-23 at 17:26 -0500, Randy Carpenter wrote:
> One major issue is that there is no way to associate a user's MAC (for
> IPv4) with their DUID. I haven't been able to find a way to account
> for this without making the user authenticate once for IPv4, and then
> again for IPv6. This is cumbersome to the user. Also, in the past
> there have been various reason why we want to pre-authenticate a
> client's MAC address (mostly for game consoles, and such, which have
> the MAC written on the outside of the machine). How can this be done
> with IPv6, which the DUID is not constant?

Perhaps I misunderstand you (or the RFCs) but it seems to me that the
DUID *is* constant. Reading section 9 of RFC 3315, it's pretty clear
that a DUID is generated once, according to simple rules, and does not
change once it has been generated. Barring intervention, of course.

The problem is how to either find out ahead of time what DUID a client
has OR how to impose a specific DUID on a client as part of provisioning
it. Neither of those issues looks particularly intractable, especially
if vendors start shipping with pre-configured DUIDs that are written on
the boxes.

What do you mean by "authenticate"? Do you mean something like 802.1x?

Regards, K.

Karl Auer (kauer at

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