Two subnets, one with PXE clients

Simon Hobson dhcp1 at thehobsons.co.uk
Wed Mar 3 15:56:04 UTC 2010


At 09:49 -0500 3/3/10, Osmany wrote:

>authoritative;
>ddns-updates on;
>ddns-update-style interim;
>ddns-domainname "oc.quimefa.cu.";
>ddns-rev-domainname "in-addr.arpa.";
>ignore client-updates;
>include "/etc/bind/rndc.key";
>
>zone oc.quimefa.cu.{
>         primary 127.0.0.1;
>         key rndc-key;
>}
>
>zone 4.25.10.in-addr.arpa.{
>         primary 127.0.0.1;
>         key rndc-key;
>}
>
>option domain-name "oc.quimefa.cu";
>option domain-name-servers 10.25.4.8;
>option ntp-servers 10.25.4.6;
>option ip-forwarding off;
>
>default-lease-time 600;
>max-lease-time 7200;
>
>log-facility local7;
>
>class "PXEClients" {
>        match if substring (option vendor-class-identifier, 0, 3)="PXE";
>        one-lease-per-client on;
>        next-server 192.168.0.2;
>        filename "/ltsp/pxelinux.0";
>        option root-path "/opt/ltsp/i386";
>        allow booting;
>        allow bootp;
>}
>
>subnet 10.25.4.0 netmask 255.255.255.0 {
>         option routers 10.25.4.1;
>         option broadcast-address 10.25.4.255;
>         one-lease-per-client on;
>         pool{
>   range 10.25.4.20 10.25.4.46;
>   range 10.25.4.48 10.25.4.51;
>   range 10.25.4.53 10.25.4.78;
>   range 10.25.4.80 10.25.4.94;
>   range 10.25.4.96 10.25.4.170;
>   range 10.25.4.172 10.25.4.210;
>   range 10.25.4.212 10.25.4.229;
>   allow unknown-clients;
>   deny members of "PXEClients";
>         }
>}
>
>subnet 192.168.0.0 netmask 255.255.255.0 {
>         pool{
>         range 192.168.0.3 192.168.0.50;
>         allow members of "PXEClients";
>         }
>}
>
>when I add the second IP to the interface the dhcp3-server does not
>start and I get this in the syslog:
>
>Internet Systems Consortium DHCP Server V3.1.1
>Mar  3 09:46:28 apolo dhcpd: Copyright 2004-2008 Internet Systems
>Consortium.
>Mar  3 09:46:28 apolo dhcpd: All rights reserved.
>Mar  3 09:46:28 apolo dhcpd: For info, please visit
>http://www.isc.org/sw/dhcp/
>Mar  3 09:46:28 apolo dhcpd: Wrote 0 class decls to leases file.
>Mar  3 09:46:28 apolo dhcpd: Wrote 197 leases to leases file.
>Mar  3 09:46:28 apolo dhcpd: Interface eth2 matches multiple shared
>networks


As I wrote on the 20th Feb :
>From the way it's phrased, I assume both sets of clients are on the 
>same physical network ? Ie, a machine may boot into PXE and get one 
>address, then boot into Windows with the same network cable and get 
>a different address.
>
>If this is the case, then you have a shared network and MUST 
>configure the server accordingly.

You need a shared network declaration :

shared-network "some-random-text" {
   subnet 10.25.4.0 netmask 255.255.255.0 {
     ...
   }

   subnet 192.168.0.0 netmask 255.255.255.0 {
     ...
   }
}

Without this declaration, you are telling the server that you have 
two DIFFERENT networks with those IP subnets on them. Internally, 
each subnet is put in a shared network with one member (I guess it's 
easier to do that than to have two code threads depending on 
presence/absence of shared network). You you did in fact have two 
shared networks matching one interface.

By using the shared-network declaration, you are telling the server 
that both IP subnets are on the same physical wire.

Looking back I see that I managed to omit to state that you nbeed to 
use "shared-network" which of course you would then have found in 
"man dhcpd.conf".

-- 
Simon Hobson

WANTED: "Software CD ROM Kit" for Canon CLBP 360-PS printer (Canon 
part no RH6-3612, or possibly RH6-3810, or RH6-3610 might do). I've a 
dead HD and need this CD so I can replace the disk and re-install the 
printer OS on it.
This is NOT the same thing as the printer drivers to load on the 
computer - there's no problem there.
If anyone knows where I might get hold of one I'd be grateful - 
requests to Canon drew a blank, it's been out of support for years.
Alternatively, if anyone has one of these and would let me image 
their hard disk ...

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.



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