bridge question

Bonjour,

I know almost nothing about bridges and I try to setup an install which
uses bridge.

I have a private network on my eth1 interface and I want to have both
thin clients and computers to able to use the same eth1.

I am under fedora 10 and installed ltsp packages for thin clients,
following the instructions on:
https://fedorahosted.org/k12linux/wiki/InstallGuide

In this guide they explain how to setup a bridge for the TC:

ifup ltspbr0
brctl addif ltspbr0 eth1


And it works, TC can boot on 172.31.100.0 network.

Now I have a dhcp server on my private network for the "normal"
computers also, which use 192.168.1.0 network and I want to have both
networks enabled in the dhcpd.conf; here is what I have done in this
config file:

<----dhcpd config begins
<snip> (usual declarations)

#Le réseau ltsp:

shared-network LTSP {
subnet 172.31.100.0 netmask 255.255.255.0 {
#range dynamic-bootp 172.31.100.100 172.31.100.253;
use-host-decl-names on;
next-server 172.31.100.254;
option log-servers 172.31.100.254;
# PXE
if substring (option vendor-class-identifier, 0, 9) = "PXEClient"
{
# NOTE: kernels are specified in /tftpboot/ltsp/i386/
pxelinux.cfg/
filename "/ltsp/i386/pxelinux.0";
} else {
option root-path "172.31.100.254:/opt/ltsp/i386";
#option root-path "nbd:172.31.100.254:2000:squashfs:ro";
}
host NEO-51B5F4 {
hardware ethernet 00:e0:c5:51:b5:f4;
fixed-address 172.31.100.100;
}
<snip>
}
}

#Et l'autre réseau:

subnet 192.168.1.0 netmask 255.255.255.0 {
# option subnet-mask 255.255.255.0;
option routers 192.168.1.1;
# next-server 192.168.1.1;

group{
use-host-decl-names true ;
host bhaskara2 {
hardware ethernet 00:09:5b:1e:a0:23;
fixed-address 192.168.1.3;
}
<snip>

}# fin group
}# fin subnet

<---- dhcpd config ends


This works in a way: both TC and computers can boot and computers get
their IP address and name from dhcp server but computers cannot use the
network which remains unreachable for them after they got their correct IP.

If I disable the bridge (brctl delbr ltspbr0), they can use the network
without any problem.... but the TC not.

I also use iptables to forward the private lan to the internet through
an eth0 interface.


Is there a way to setup these two networks altogether? And how?

My lack of knowledge about bridges does not allow me to solve this
problem and, even, to answer the question: is that possible?

I read some howto on the internet, but it seems to me that the described
bridges are set in another way (using two "real" interfaces).


Thanks for any help.


--
François Patte
Université Paris Descartes