Linux DHCP options (PXE) without IP

Levi Pearson levipearson at gmail.com
Wed Oct 6 12:00:55 MDT 2010


On Wed, Oct 6, 2010 at 11:34 AM, Eric Olsen <falconv at gmail.com> wrote:
> Hi all,
>
> I have other ways I can do this that are fine, but out of curiosity I wanted
> to investigate this path:
> At home I'm interested in setting up a PXE boot server to make it easier to
> set up my laptops that otherwise would have to be plugged into the docking
> station to have a DVD ROM to boot from (which is hard to do with the one I
> modified to be in a picture frame ;) ). I'm familiar with a Windows PXE
> server because I support it at work, which will respond to PXE Client
> requests with the PXE DHCP options only, and let DHCP assign the IP. I don't
> have a Windows server at home, so I'm looking at setting up a Linux PXE
> server.
>
> All Linux PXE tutorials I've found so-far instruct to modify DHCP to include
> the PXE options. That makes sense, I've done that before, but at home I am
> using a not-so-robust DHCP (built into my router) which unfortunately
> doesn't give me much control over the DHCP options.
>
> As I said, I have other ways to do this, i could turn off DHCP on the router
> and set it up on my server, but I'm curious if this would be possible. I'd
> like to set up DHCP on my server, but configure it to ONLY give the PXE
> options to PXE clients, and allow the router's DHCP to assign the IP.

DHCP has a mechanism called DHCPINFORM for a client to request boot
parameters when it already has an IP address.  But there's no reason
you couldn't have two DHCP servers giving out IP addresses.  Despite
the trouble it can cause when it happens unexpectedly, DHCP is
designed to work with multiple servers on a network, even when their
ranges overlap. Clients can choose between leases offered to them, and
the DHCPREQUEST is broadcast so that other servers know they were not
chosen and what the identity of the chosen server is.

So, you'll definitely be running a DHCP server on the boot server
machine, but how you configure it will depend on the flexibility of
the PXE client and the DHCP server software you use.

        --Levi


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