AW: MAC vs DUID issue

Albrecht, Harald harald.albrecht at
Thu Apr 3 07:54:40 UTC 2014

What's bad about the DUID-LL?

> -----Ursprüngliche Nachricht-----
> Von: at
> [ at] Im
> Auftrag von sthaug at
> Gesendet: Mittwoch, 2. April 2014 21:38
> An: dhcp-users at; dhcp1 at
> Betreff: Re: MAC vs DUID issue
> > There have been "vigorous discussions" before about MAC vs GUID ! My
> understanding was that the MAC is not delivered in the DHCPv6 packets and
> are not available to the server to use. The reason for this is that those who
> designed the spec felt that MAC addresses have several flaws - there can be
> more than one per device, and they can change due to hardware changes.
> The counter point (to which I subscribe) is that while MACs have issues, they
> are for many the least bad option since they are fairly invariant, remain
> across multiple OSs and OS reinstalls (and in your case, 'careless' cloning).
> I agree with this point of view too - it was a serious mistake to drop the MAC
> address.
> > IIRC there was talk of defining an option to carry the MAC address, but I
> can't remember what the outcome was, and in any case it could be "some
> time" (if ever) before all devices send it.
> RFC 6939 (DHCPv6 Client Link-Layer Address Option). Unfortunately, I don't
> know of any equipment which implements this yet. Also, note that this
> option is *only* meant for relay agents. On other hand - if your
> DHCPv6 client is on the local LAN, you can of course look at the source MAC
> address directly...
> There's been some spirited discussion about this on Nanog recently, see for
> instance
> Steinar Haug, Nethelp consulting, sthaug at
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