[Udpcast] Question on DHCP/BOOTP and PXE

Jaco Kroon jkroon at cs.up.ac.za
Tue Oct 26 20:16:32 CEST 2004

Donald Teed wrote:

> I've scanned the man pages for dhcp and saught for
> a howto on bootp with rarp and I can't find an answer/solution.
> I want to set up a PXE boot server on a network where I should work with
> an existing DHCP server but I cannot configure that DHCP server.
> There is a Windows based PXE server on that
> network which can take a given floppy and make it into
> a PXE bootable option from the menu.  It uses
> "DHCP proxy" to refer to the real DHCP server.
> I've looked for an option like that for ISC DHCP but
> can't spot it.
> I've also checked out bootpd and rarpd.  I've used it before
> to boot a single machine with a Linux kernel, but I don't
> think it has the features to support a PXE boot environment for
> any of the possible 4500 client machines on the network.
> If anyone has a hint on how either of these approaches could work
> to provide only PXE boot but either pass on or ignore
> DHCP address requests, I'd like to hear of it.  Or otherwise
> something different.  I'm working with floppyless notebooks,
> and we'd rather not require CDs for booting either.
> --Donald Teed

PXE relies on dhcp/bootp, specifically you want to be able to configure 
the "next-server" and "filename" options, which tells PXE where to find 
the image to boot.  So unless whoever controls the dhcp server is 
willing to add these options for you you are going to have a hard time.  
>From there on you should take a look at pxelinux which wich provides you 
with a lilo like boot loader that loads from the network.  I've managed 
to make udpcast work from rootnfs this way.

As far as I understand it PXE sends out a standard DHCP request, the 
response then contains the next-server and filename options which PXE 
then uses - if these options are not set, PXE terminates.


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