[K12OSN] DHCP and PXE with two different Class of IP

Theo Turner Theo.Turner at CumnorHouse.com
Sat Dec 9 10:01:33 UTC 2006

I know the problem well of a spread out network needing clients over the
same lan cabling as the existing network. 

This is the solution I have in place at the moment.

I am using a K12LTSP V5 with a fairly standard install. I.e it has 2
nics and is set up for LTSP, but I don't actually plug anything into the
client nic. I connect all my clients using the nx client. Another reason
I do this is because I have this set up in a school that is still very
dependant on windows. I have so far half converted the preprep. So I
need to have the ICT lab capable of switching from Windows to Linux and
back very quick.

My solution is to use the free nx server on the K12 box and then use the
windows client. To make this kidy friendly I have changed the windows
GUI for a user called 'kid' to a custom one I modified from some
downloaded vb source code. When this user logs on they have a logoff
button at the bottom of the screen and an Icon to launch the nx client
with the settings and password already entered. This complete log on
(windows and nx) takes 15seconds even when a class of 20 come in at
once. Everything works great, screen refresh is fast, much faster than
VNC even over local network. Even sound works so everyone is happy. I
have joined the K12 box to the windows 2K domain so staff can access
their network documents etc. But the preprep children's accounts are
local so as not to make the system dependant on the windows domain at
all. This side of the system works brilliantly and bar a niggle or two
over a couple of specific apps I am very pleased. 

Using a linux based client has so far defeated me in terms of sound. But
I haven't spent long on it yet and was hoping for some help from this

I did upgrade a couple of the backbone switches to gigabit to ensure
enough bandwidth although I am fairly sure everything would have
continued much the same without it.

Good luck, I hope something here helps 
Theo Turner

-----Original Message-----
From: k12osn-bounces at redhat.com [mailto:k12osn-bounces at redhat.com] On
Behalf Of Bert Rolston
Sent: 09 December 2006 07:28
To: k12osn at redhat.com
Subject: Re: [K12OSN] DHCP and PXE with two different Class of IP

Hi David,

That's the kicker.

The K12LTSP internal nic WILL be on the same physical network as the MS
Class B dhcp server.

My gut instinct is to modify K12LTSP to work with the CLASS B

In other words let the MS DHCP server dish out the addresses. BUT as I
have read here in the past, this poses a problem with redirecting PXE
requests to the K12LTSP server. Or has this issue been resolved?

Bearing in mind I might not be allowed to make changes to the MS DHCP
server, I was looking for an alternative. 

Unfortunately, the terminals will be spread ALL OVER campus, not in a
single lab where I could throw in another switch and repatch the lab
machines onto that switch. :-(

So if anyone has run into a similar situation I would appreciates some

At this stage I don't even know the full layout of the network.

Thanks again David, 
and the list.

Bert Rolston

> ------------------------------
> Message: 2
> Date: Fri, 8 Dec 2006 09:00:32 -0500
> From: "David Whitmer" <thewhitmers at gmail.com>
> Subject: Re: [K12OSN] DHCP and PXE with two different Class of IP
> 	address
> To: "Support list for open source software in schools."
> 	<k12osn at redhat.com>
> Message-ID:
> 	<a28861770612080600p19ae4a4ci6e00f024384634a0 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> On 12/7/06, Bert Rolston <bert.rolston at clear.net.nz> wrote:
> > Thanks John,
> >
> > <snip>
> >
> > But back to the question.
> >
> > So what you were saying earlier is that on the K12LTSP server I set
> >        - 1 NIC with a Class B address that matches their scheme,
> >          connected to their physical media
> >        - 1 NIC with the standard K12LTSP Class C scheme connected to
> >          the same physical media, through the same switch
> >
> > This should satisfy my customer's criteria.
> >
> > What will the MS DHCP server do when a PXE request comes from the
> > hardware?
> >
> > I may be answering my own question, as I understand things MS DHCP
> > ignore the request. Is that the case?
> >
> > As for the LTSP DHCP server, I take it I can tell it to IGNORE any
> > requests from a host with an MS operating system.
> >
> > Thanks for your time.
> >
> > Cheers,
> > Bert
> >
> Bert,
> As long as the PXE-booting computers are connected to the same
> physical network connected to the K12LTSP server's "internal" NIC, the
> PXE request will stop at that server and not go out to your class B
> network.
> Also, the NIC connected to the class B network will not be running
> DHCP service... the K12LTSP server by default only runs that for the
> internal network NIC.
> In your e-mail, it looks like you're planning to connect both of the
> NICs in the K12LTSP server into the same network switch.  That will
> cause you problems.  The default K12LTSP setup is meant to have the
> server act as a gateway/router between two physical networks, one for
> your thin client (PXE booting) computers, and the other your main
> network.
> David Whitmer
> Director of Media & Technology
> Calvary Schools of Holland (Michigan)
> web: www.calvaryschoolsholland.org
> email: thewhitmers at gmail.com

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