PXE only Config [OT]

Daniel Wells daniel_wells at byu.edu
Mon Dec 3 21:54:08 UTC 2007

So yes,

Thanks for the clarification.  The technical name is a DHCP proxy.  So are you saying that ISC DHCP cannot be configured as a Proxy DHCP or that it is just difficult.  It seems that the main difference is that the proxy can reply with a null client IP address field (from the spec," If this is a Proxy DHCP Service, then the client IP address field is null (").

There is great diagram in the PXE spec (v 2.1) that illustrates exactly what we want.

"Figure 2-4 illustrates the case of a Proxy DHCP service and the DHCP service on different servers. In this case, the Proxy DHCP service listens to UDP port (67) and responds in parallel with the DHCP service."

I apologize for the confusing term "PXE server".  I hope this clarifies things.

That being said, does anyone know of any documentation that might discuss setting up ISC DHCP as a proxy DHCP?

    - Daniel Wells

-----Original Message-----
From: dhcp-users-bounce at isc.org [mailto:dhcp-users-bounce at isc.org] On Behalf Of Bruce Hudson
Sent: Monday, December 03, 2007 2:22 PM
To: dhcp-users at isc.org
Subject: Re: PXE only Config [OT]

> P.S. But, at first glance I believe this option is more relevant for the
> client request, not the server response.

    Normally you are correct, the client includes a parameter request list
in the REQUEST. However, some clients expect parameters they do not ask for
so it is possible to edit the list on the server.

    However, I am not sure this will help you. The "Client IP" is not an
option so it does not have an option number to be requested. Nor is the
"filename", although there is an option to over-ride that.

    Reading the PXE spec somebody posted earlier in this thread, PXE knows
three types of servers: DHCP, "proxy DHCP" (also known as a redirection
service?), and "Boot".  Despite the name and the fact that a "proxy DHCP"
server communicates via the DHCP protocol, it is not a DHCP server. The
spec specifically states that given two DHCP servers, the client must take
all options from one reply; which specifically forbids what you are trying
to do.

    It appears to me that you are trying to configure the DHCP server to be
a PXE "proxy DHCP" server rather than a DHCP server. That is likely to be
more than a configuration option. Personally, I think the naming convention
in the PXE spec was unfortunately confusing.
Bruce A. Hudson                         | Bruce.Hudson at Dal.CA
UCIS, Networks and Systems              |
Dalhousie University                    |
Halifax, Nova Scotia, Canada            | (902) 494-3405

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