DHCPv6 and MAC Address inclusion

perl-list perl-list at network1.net
Thu Jan 26 17:53:22 UTC 2012

----- Original Message -----

> From: "Ted Lemon" <Ted.Lemon at nominum.com>
> To: "Users of ISC DHCP" <dhcp-users at lists.isc.org>
> Sent: Thursday, January 26, 2012 12:11:49 AM
> Subject: Re: DHCPv6 and MAC Address inclusion

> On Jan 25, 2012, at 3:54 PM, perl-list wrote:
> > Authenticating them once is fine. We are talking twice here since
> > the customer will have to authenticate the DHCPv4 and the DHCPv6
> > since there isn't a way to tell that they are the same device.

> Presumably you are doing this with a captive web portal of some sort.
> It shouldn't be a problem to do the authentication step over both
> IPv4 and IPv6 at the same time; this should establish that the two
> devices are the same device, and then you can just keep a record of
> the identifiers the device was using for future reference.
Don't know how one would do that. At best, potentially we could cause the web browser to immediately connect to the IPv6 address of the web portal transmitting the same information (so that the web portal had the IPv6 address). This would cause a nice failure error message in clients that don't have IPv6 enabled, or aren't even capable of IPv6. 

> > And why should anyone care about a DUID and IAID and whether they
> > are present or not? These bits of info are not necessary for
> > networking to function.

> They are necessary for DHCP to function in conformance with the
> standard.
So they need to exist so that they can exist? Sounds like a circular argument. 

> > I seriously doubt anyone is going to change the format / generation
> > logic of the UID from DHCPv4 on their client. That would be a
> > great solution in the case it were done.

> Yup.

> > This information is not always available. Not all DSLAMs support
> > this. Not all relay agents support this. Authentication of some
> > kind must be used in most cases save cable modems.

> This doesn't match with what I'm hearing. I think it depends on your
> circumstances. Where would you find a DSLAM that both supports IPv6
> and doesn't have this feature? Or are DSLAMs strictly layer 2?
Whether they are layer 3 or layer 2 doesn't really matter. The simple fact is that varying manufacturers implement useful features to varying degrees or not at all. Much like the MAC address in the DHCPv6 packet, it cannot be counted upon that a particular DSLAM will have some certain functionality available that will make your life easier. 

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