DHCP on router and BOOTP on server. Is it possible?

Glenn Satchell Glenn.Satchell at uniq.com.au
Tue Aug 4 00:16:36 UTC 2009

>Date: Mon, 3 Aug 2009 22:43:30 +0300
>Subject: DHCP on router and BOOTP on server. Is it possible?
>From: äÍÉÔÒÉÊ ûÕÍÉÌÉÎ <sdv.brest at gmail.com>
>To: dhcp-users at lists.isc.org
>X-BeenThere: dhcp-users at lists.isc.org
> Hi, ISC DHCP users!
> In short, my target is to add ability of booting thin clients from netboot
> server (server with running on it TFTP, NFS, DHCP) without making changes or
> disabling DHCP server running on router.
> Is it possible to configure DHCP server in way, so DHCP server will be
> responsible for providing ONLY data regarding network boot and getting all
> other data (IP address, netmask, gateway, etc) from DHCP running on router
> and providing all data together to client.

Depends on how configurable your router's dhcp server is. For example,
in ISC dhcp you can specify thgat the tftp server is another system.

But generally there is no way, without re-writing the code, that one
dhcp server can aggregate information from two different sources to
return a dhcp response.

> Maybe there are some other ways of adding netboot ability to my network
> without changing currently running DHCP server?

Essentially you need a way to identify netboot requests, and respond to
that, but ignore other dhcp requests. There are a few ways to do this
with ISC dhcp. So you need to see if there is some option, or a known
MAC address prefix you can filter against, or are they all on one
subnet, for example?

Likewise on the router, it needs to ignore these clients and respond to
all other requests. This is the key to whether it is achievable,
otherwise your netboot clients will get two responses, and they get to
choose which one they use. The response from ISC dhcp will allow them
to boot, the other probably not.

So defining a class to match your thin clients only is needed. Are they
all the same brand? If so then you might be able to use a common MAC
address prefix, eg:

class "netboot-clients" {
	match if (substring(hardware, 1, 3) = aa:bb:cc);
subnet ( ... ) {
	pool {
		range ...
		allow members of "netboot-clients";

Note no quotes around the mac address prefix as we are doing a binary

> I got work netboot before with ISC DHCP server WITHOUT router’s DHCP and now
> I need to make it work together with router’s DHCP.

In the end it's probably going to be easier to just pick one dhcp
server or the other and go with that. Is there some political or
business reason why you can't have a dhcp server not running on the
router? Let me guess, the network guys run the dhcp service, and you've
just been given responsibility for all these new thin clients? :)

> Thanks in advance.


Glenn Satchell     mailto:glenn.satchell at uniq.com.au | I telephoned the
Uniq Advances Pty Ltd         http://www.uniq.com.au | swine flu info
PO Box 70 Paddington NSW Australia 2021              | line and all I got
tel:0409-458-580  tel:02-9380-6360  fax:02-9380-6416 | was crackling.

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