DHCPv6 and MAC Address inclusion

scott_stone at trendmicro.com scott_stone at trendmicro.com
Thu Jan 26 05:20:07 UTC 2012

It's been a while since I worked at 2Wire, but while there I did manage several DSLAMs for the testing/QA lab.  A DSLAM itself is a layer 2 device - layer 3 is handled by something called an "access concentrator".  That said, some vendors (the Cisco 6400 units that I had there) combine the 2 into a single chassis (kind of like a layer 3 routing switch, except for the DSL world).  Canonically speaking though, a DSLAM itself is like an ethernet switch in that it is simply a layer 2 device.

Unless things have changed in the last few years?

Scott Stone <scott_stone at trendmicro.com>
Manager, DCS-RD
Trend Micro, Inc. http://www.trendmicro.com

-----Original Message-----
From: dhcp-users-bounces+scott_stone=trendmicro.com at lists.isc.org [mailto:dhcp-users-bounces+scott_stone=trendmicro.com at lists.isc.org] On Behalf Of Ted Lemon
Sent: Wednesday, January 25, 2012 9:12 PM
To: Users of ISC DHCP
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.

> 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.

> 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.


> 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?

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