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[K12OSN] Followup on prior discussion on dualing DHCP servers, MS and K12LTSP



I found the following on the K12OSN listserv from May of last year. At
the time the comment was "this is alpha". Have people been using this
successfully to allow dualing DHCP servers on the same subnet to support
the Microsoft and K12LTSP terminals?


-- 

Thanks,

John

The irony is that Bill Gates claims to be making a stable operating
 system and Linus Torvalds claims to be trying to take over the world.
                - Mattrol uscom com (Drakmere)

<< Email copied below >>
Steve Wright  k12osn redhat com
Fri May 31 21:48:01 2002

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jam McQuil com wrote:

[snip]

I Think I have a working solution.

I had a dig through a working w2k box, and it is indeed possible to ;

a.)    de-allocate a DHCP IP range so that LTSP can function on that
range.

b.)    de-allocate a vendor-ID string so the w2k DHCPd will *not*
respond to
        requests from;

        1.)    Etherboot DHCPClients
        2.)    PXEClients
        3.)    Linux `dhcpcd eth0`

This will stop booting LTSP clients from inadvertantly getting a useless
lease from the w2k box.

The next problem is - Booting Win95/98 clients on the same subnet may 
get issued a lease from the Linux system.

This is not a problem, at first glance, but then;  We quickly run out of
addresses if there are more than 100 clients
on a Class-C subnet (think about it..8-)

So on the Linux DHCPd we have to `deny booting;` where vendor-identifier
== a Microsoft Client.

So /etc/dhcpd.conf looks like this..

shared-network WORKSTATIONS {
  subnet 192.168.0.0 netmask 255.255.255.0 {
     range dynamic-bootp 192.168.0.100 192.168.0.253;
     use-host-decl-names       on;
     option log-servers        192.168.0.254;

     # trick from Peter Rundle <peter rundle au interpath net>
     if substring (option vendor-class-identifier, 0, 9) = "PXEClient"
     {
        filename      "/lts/pxe/pxelinux.bin";
          # NOTE: kernels are specified in
/tftpboot/lts/pxe/pxelinux.cfg/
     }
     else
     {
        filename    "/lts/vmlinuz-2.4.9-ltsp";
     }

------------ add this bit

     # trick from Steve Wright <paua quicksilver net nz>
     # If your LTSP system shares a subnet with a NT4 or W2K server
     # uncomment the following.
      if substring (option vendor-class-identifier, 0, 4) = "MSFT"
     {
       # Windows 95/98/NT/2k Calling. Don't respond.
       deny booting;
     }

--------------- done. dhcpd.conf continues..

  }
}

...


and ??

It ROCKS !  WooHoo !!

disclaimer: This is barely alpha quality.

Peer review, please..

Complete HOWTO to follow.

share and enjoy.
/Steve











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