[Dnsmasq-discuss] DHCPv6 and MAC

[Gene Czarcinski]

On 02/11/2013 12:13 PM, Dan Williams wrote:
> The option you're looking for*is*  to set default-duid in the lease
> file.  That's exactly how you tell NM to use the DUID you want.
> Otherwise, NM will generate the DUID-UUID.
See my other message.  This appears to be not working.

Do you want me to create a bugzilla report on this?
>
> As I mentioned in other mails to this thread, the DUID-UUID gets used
> for a number of reasons (all quotes from RFC 3315):
>
> 1) the RFC specifies that the DUID is*per machine*, not per-interface,
> and that one DUID is used for any client run on that machine.
> Furthermore, "the DUID must be globally unique".
Well, actually, I believe it says "per device".  Also, RFC6355 says that 
the only solution they consider is firmware based which /etc/machine-id 
is not or it would not vary between OS installs.
>
> 2) A machine may contain more than one network interface and since under
> Linux, interface enumeration is not stable, there's no way to
> consistently choose which interface to use for the DUID-LL.  Since the
> RFC indicates that the same DUID should be used for all interfaces
> ("each DHCP client and server should have exactly one DUID"), it's
> really a toss-up which interface is the "main" interface from which we
> should generate the machine-wide DUID.
>
> 3) Since the RFCs state that the DUID should not change as a result of
> changes to network interfaces, addition/removal of hardware, etc ("a
> device's DUID should not change as a result of a change in the device's
> network hardware") this implies that it must be stored somewhere.  This
> causes a problem when network booting or cloning system images, since a
> stored DUID would be used for all machines and would no longer be
> globally unique as required by #1.  Since /etc/machine-id is already
> supposed to be globally unique, it must already be handled by the
> cloning/network-boot case, and thus we can use it as a basis for the
> DUID-UUID without creating extra work for the administrator.
>
> But again, you're free to override this behavior by modifying the
> default leasefile in /etc/dhclient6.leases with whatever DUID you
> desire.
I had considered /etc/dhclient6.leases and rejected it but I do not 
remember why.  Now, it seems like the "right" solution.  Since almost 
all my installs use kickstart, I could set this in my post-install script.

I think I have beaten this dead horse more than enough.

Gene