DHCPv6 client classification based on DUID.

Simon Hobson dhcp1 at thehobsons.co.uk
Thu Sep 20 20:52:25 UTC 2012

Ted Lemon wrote:
>On Sep 20, 2012, at 2:37 PM, "Alex Bligh" <alex at alex.org.uk> wrote:
>>  Has anyone worked out how (e.g.) PXEboot would work with IPv6? I presume
>>  it would need to generate the DUID and some how magically pass this to
>>  the host OS.
>Section 7 of RFC4361 speaks to this question.

Well sort of, but it's not really that specific - nor can it be 
unless you can get multiple hardware and software vendors to 
co-operate. In the general case, the first stage boot is likely to 
not have access to an OS specific DUID - and vice-versa.

That's only likely to change if hardware vendors start providing a 
specific place to store a device-wide DUID, and software vendors 
support using it. I don't see that happening soon.
 From the system administrators POV, the best thing to do is detect 
PXE (and similarly transient) clients and restrict their lease 
lengths. But given the vast address space available in IPv6 where in 
effect a single subnet may have many times more addresses than there 
are in total in the IPv4 address space, I don't see it being an issue 
for PXE etc clients to tie up a few addresses.

Simon Hobson

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