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



Well you should be able to set up the LTSP server as a NAT firewall through 
IPTables, or use a hardware NAT firewall in front of the server; that way you 
can hide the terminals behind the server's IP address and still make no 
changes to the rest of the network, while still enabling you to run your own 
DHCP server for the terminals. 

BTW, a single net class B means that *all* hosts are in the same broadcast 
domain. If you have over 250 hosts on that net, that is a lot of broadcast 
traffic, one chattering NIC and the entire net feels the pain. I wouldn't 
want to be a network support tech on that net if anything goes wrong; that 
isn't the most robust net design. A netmask of 20 bits would allow 16 subnets 
of 1024 hosts each and allow sub-dividing the broadcast domain and isolate 
traffic behind routers (as well as allow special subnets like yours without 
resorting to NAT).

On Thursday 07 December 2006 16:44, Bert Rolston wrote:
> Hi John,
>
> Thanks for your reply.
>
> The reason they went to a Class B scheme was to overcome the 254 host
> limit.
>
> They are using a /16 subnet mask.
>
> The network in question is at a small tertiary educational
> establishment. It provides courses in business studies ( 1 lab),
> animation ( 2 labs), certificate in television production, christian
> ministry and counselling courses. Also running on the same network are
> campus admin, a small regional TV station, TV production and marketing
> company, an animation studio with render farm.
>
> Thanks for your time,
> Bert
>
> On Thu, 2006-12-07 at 12:54 -0400, John Lucas wrote:
> > You mentioned that the current network is using a class B address scheme,
> > but is that address space sub-divided? What netmask is being used?
> >
> > Almost no one with a class B uses the 16-bit netmask; use of a 24-bit
> > netmask divides the single network into up, to 254 subnets of up to 254
> > hosts each (a more useful scheme). Assuming that a 24-bit (or larger)
> > netmask *is* being used, how about creating a new private (class-C sized)
> > subnet on one NIC in an LTSP server, and have another NIC attached to the
> > existing network? This allows the terminals to use
> > DHCP/tftp/PXE/etherboot from the LTSP server and still access the MS
> > Terminal server (using rdesktop) without changing the existing network
> > (save for the addition of the new LTSP server and it's terminals). In
> > this scenario the LTSP server could be used as a router (for terminals
> > running rdesktop sessions), or as a dual-homed host (running rdesktop
> > from the LTSP server itself).
> >
> > My choice would be to run rdesktop on the terminal (via the SCREEN_x
> > directive in lts.conf). This allows sound to be re-directed from the MS
> > TC to the terminal and preseves the ability to run Linux on the LTSP
> > server (via a separate SCREEN_x directive). Thin clients are far simpler
> > to maintain than stand-alone PCs.
> >
> > On Thursday 07 December 2006 00:58, you wrote:
> > > Hey folks,
> > >
> > > I know this little chestnut has been chewed over many times on this
> > > list. I don't remember my situation coming up. So first I'll describe
> > > the environment.
> > >
> > > =======================
> > > The current environment
> > > =======================
> > >
> > > An MS Network with AD, terminal server and MS DHCP server with CLASS B
> > > IP address scheme.
> > >
> > > They want to revitalise their old Win 9x / NT machines and are
> > > investigating using K12LTSP or locally installed Linux. They have a lot
> > > of old classic to PII Pentiums which are gathering dust.
> > >
> > > One option is to boot the LTSP terminals in kiosk mode to access their
> > > Windows Terminal server using the RDP client included.
> > >
> > > The other option is to install a lightweight Linux distro (Puppy or
> > > DSL) on all the machines and use the RDP client that way.
> > >
> > > They don't want to change their existing infrastructure if at all
> > > possible. Even making changes to their DHCP server is considered risky
> > > by the network admin. ANY adverse impact on their existing system is
> > > unacceptable.
> > >
> > > The network admin uses Ubuntu at home, but has been unable to get any
> > > Linux computer to authenticate to the AD at work.
> > > For that reason he only sees limited potential for Linux / OSS in their
> > > current environment.
> > >
> > > Users will authenticate to their AD through Windows terminal sessions.
> > >
> > > Later on they may enable access to the Linux desktop and apps.
> > >
> > >
> > > =======================
> > > My Question
> > > =======================
> > >
> > > Given that the current DHCP server issues Class B addresses.
> > >
> > > Can the K12LTSP DHCP server, which issues Class C addresses
> > > 	- co-exist on the same physical media
> > > 	- handle PXE requests from the old hardware,
> > > 	- and not interfere with their current setup?
> > >
> > > If so what changes (if any) need to be made
> > > 	- on the MS DHCP server,
> > > 	- their current setup
> > > 	- the K12LTSP server
> > >
> > > Thanks,
> > > Bert
> > >
> > > _______________________________________________
> > > K12OSN mailing list
> > > K12OSN redhat com
> > > https://www.redhat.com/mailman/listinfo/k12osn
> > > For more info see <http://www.k12os.org>

-- 
        "History doesn't repeat itself; at best it rhymes."
                        - Mark Twain

| John Lucas                          MrJohnLucas gmail com               |
| St. Thomas, VI 00802                http://mrjohnlucas.googlepages.com/ |
| 18.3°N, 65°W                        AST (UTC-4)                         |


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