Two subnets, one with PXE clients

Osmany osmany at oc.quimefa.cu
Mon Feb 22 13:19:07 UTC 2010


On Sat, 2010-02-20 at 20:48 +0000, Simon Hobson wrote:
> <osmany at oc.quimefa.cu> wrote:
> 
> >I would like some help in configuring my DHCP. Currently I am running
> >ubuntu server 9.04 with dhcp3. I have successfully configured it with
> >dynamic dns updates. Recently I had to install and configure an LTSP server
> >but I would like to use the same DHCP to assign IP addresses to he PXE
> >Clients but here is the thing; I would like to work with the PXE Clients on
> >the same physical network but on a separate subnet. For example I would
> >like the windows XP clients to work on the 10.25.4.0/24 subnet and the PXE
> >Clients to work on the 192.168.0.0/24 subnet, of course I have a second NIC
> >installed and configured.
> 
>  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 do NOT need a separate network card for this, and in fact it will 
> complicate matters if you do. You can add multiple IP addresses to 
> one interface, use the "ip" command to do this, eg "ip addr add 
> 192.168.0.1/24 dev eth0" will add 192.168.0.1 to whatever is already 
> configured on eth0. Ubuntu is Debian derived, so you can add this to 
> /etc/network/interfaces to have it done automatically :
> 
> auto eth0
> iface eth0 inet static
>    address 10.25.4.1
>    netmask 255.255.255.0
>    up ip addr add 192.168.0.1/24 dev eth0
> 
> 
> 
> >I was thinking about it and I came up with some thing like this:
> >
> >authoritative;
> >default-lease-time 600;
> >max-lease-time 7200;
> >log-facility local7;
> >ddns-updates on;
> >ddns-update-style interim;
> >ignore client-updates;
> >
> >
> >include "/etc/bind/rndc.key";
> >
> >zone domain.{
> >         primary 127.0.0.1;
> >         key rndc-key;
> >}
> >
> >zone 4.25.10.in-addr.arpa.{
> >         primary 127.0.0.1;
> >         key rndc-key;
> >}
> >
> >include "/etc/bind/rndc.key";
> >
> >zone domain.{
> >	primary 127.0.0.1;
> >	key rndc-key;
> >}
> >
> >zone 4.25.10.in-addr.arpa.{
> >	primary 127.0.0.1;
> >	key rndc-key;
> >}
> >
> >subnet 10.25.4.0 netmask 255.255.255.0 {
> >	option ntp-servers 10.25.4.6;
> >	option ip-forwarding off;
> >	option domain-name "oc.quimefa.cu";
> >	option domain-name-servers 10.25.4.8;
> >	ddns-domainname "domain.";
> >	ddns-rev-domainname "4.25.10.in-addr.arpa.";
> >	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 10.25.4.172 10.25.4.210;
> >	range 10.25.4.212 10.25.4.229;
> >	option routers 10.25.4.1;
> >	option broadcast-address 10.25.4.255;
> >	deny members of "PXEClients";
> >}
> >
> >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 192.168.0.0 netmask 255.255.255.0 {
> >	option subnet-mask 255.255.255.0;
> >	option broadcast-address 192.168.0.255;
> >	range 192.168.0.4 192.168.0.50;
> >	allow members of "PXEClients";
> >}
> 
> Close. Assuming you do have a shared network, then you MUST configure 
> your subnets like this :
> 
> shared-network "any-old-name" {
>    subnet 10.25.4.0 netmask 255.255.255.0 {
>      ...
>      deny members of "PXEClients";
>    }
>    subnet 192.168.0.0 netmask 255.255.255.0 {
>      ...
>      allow members of "PXEClients";
>    }
> }
> 
> Without the shared network declaration, when a PXE client attempts to 
> get an address, it will initially be offered one, but when it sends a 
> DHCP-Request for it, the server will send a DHCP Nack in response 
> because the address won't be valid for the 10.25.4.0 subnet. 
> Similarly, any requests by other clients will get a nack because the 
> address won't be valid for the 192.168.0.0 subnet.
> 
> -- 
> Simon Hobson
> 
Thank you very much Simon. That's exactly what I had in mind. I'll give
it a try later on today and will post my results.




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