Re: [dhcwg] Is DHCP supported by WinPE

On Wed, Feb 22, 2006 at 03:33:04PM +0530, Raj Bhino wrote:
> Is DHCP supported by WinPE. Can DHCP work in configuring WinPE Machines

WinPE certainly uses DHCP, but I don't think that's your question.

You've sort of reached the wrong group of people to ask what I think
you're trying to.

dhcwg@ietf.org is for the IETF DHC working group discussion - this is
the body that forms protocol documents (or tries to) that describes how
DHCP works.  It doesn't govern interoperability quite so directly as
one might hope, so can't answer your question.

So, you need to ask your DHCP server software manufacturer that question.

For ISC DHCP Server, which I suspect you are running, you want to
subscribe to and contact the dhcp-server@isc.org mailing list, you can
do that via this URL:

	http://www.isc.org/sw/dhcp/dhcp-lists.php

But if you were to search the dhcp-server archives, you would notice
that there are quite a few people who are having compatibility problems
with WinPE (or rather, with the combination of ISC DHCP server, PXE, and
WinPE):

	http://marc.theaimsgroup.com/?l=dhcp-server&m=108785514626892&w=2

In summary, it does manage to work once you disable ICMP echo checks
("ping-check false;") because the WinPE DHCP client supplies a
requested-address option that indicates the address assigned to PXE,
and this manages to bypass the server's enforcement of client identity
when the client slides between hardware-identified and client-identifer-
identified.  But this results in offering the client a new address upon
every reboot (because the converse isn't true: hardware-identified
clients are not given client-identifier-identified leases even if they
request them, which PXE wouldn't anyway).

Also the fact that it works is considered by ISC to be a bug...bypassing
client identification checks merely because the client used an identical
chaddr contents and requested the address is not the planned design.

ISC DHCP interprets RFC2131 to mean that DHCP clients providing client
identifiers are identified differently from a client at the same hardware
address that does not supply a client identifier.  Other servers are more
liberal in client identification, and WinPE relies upon this more liberal
interpretation in order to function (it supplies a client identifier equal
to the hardware address, and it is unable to change the address assigned
to the PXE layer, which did not supply a client identifier, so ends in
stalemate).

This is a fairly technical problem, and I doubt I've explained it
adequately.

If you have any further qeustions, I think we should take it to
dhcp-server@isc.org (if we are in fact your software vendor - otherwise
just mail me off-list).

-- 
David W. Hankins		"If you don't do it right the first time,
Software Engineer			you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins