The Problem

You need your LTSP server to both be a member of a larger network (the WAN), but you also need the server to serve your thin/fat clients (the LAN). To configure your LTSP server to serve your LAN, you need to configure the NIC facing it to have a static ip. There are 2 distinct approaches by which to set this up: Network Manager or configuring /etc/network/interfaces. Also, there are 2 common approaches to LTSP servers: you have a choice of using either 1 NIC or 2 NICs.

Should you use Network Manager or configure /etc/network/interfaces?

For "headless" servers the second method is preferred, but for schools where the teachers are working on the server it is suggest going with the first one, so that the teachers can easily see the network properties from the gnome applet (connection speed, up/down status...). Directions for both methods follow.

Set Static IP with network manager

Using a single NIC Setup

1. Start by reading this: http://www.liberiangeek.net/2012/04/setup-a-permanent-static-ip-address-in-ubuntu-12-04-precise-pangolin/ Then follow the directions provided there.

2. The "[x] Make connection available for all users" setting should be checked.

Using a two NIC Setup

1. Start by reading this: http://www.liberiangeek.net/2012/04/setup-a-permanent-static-ip-address-in-ubuntu-12-04-precise-pangolin/ to get started, but use the following specific info:

2. (you may want to name your cards, "Internal NIC" for the one that goes to your LAN and "External NIC" for the one that connects to your WAN)
3. The internal NIC should be set like in the image below:

4. 

5. Again the "[x] Make connection available for all users" setting should be checked.

   Warning: the generated /etc/dnsmasq.d/ltsp-server-dnsmasq.conf has proxy-dhcp mode enabled for the external NIC. So, clients in your "external" network will be able to be netbooted as ltsp clients. If you don't want that, you should remove the respective, "dhcp-range=192.168.3.0,proxy" line from that file by, for example, putting a "#" at the start of that line.

Set Static IP with /etc/network/interfaces method

(Don't read what's written in the http://www.liberiangeek.net/2012/04/setup-a-permanent-static-ip-address-in-ubuntu-12-04-precise-pangolin/ page, don't disable network manager like it suggests etc.) then...

Using a single NIC Setup

Put something like this in /etc/network/interfaces:

iface eth0 inet static
    address 192.168.3.3
    netmask 255.255.255.0
    gateway 192.168.3.1
    dns-search example.com
    dns-nameservers 192.168.3.45 192.168.8.10  

Using a two NIC Setup

For the internal NIC (the one that serves your clients), the entry in /etc/network/interfaces should be something like this:

• iface eth1 inet static
  address 192.168.67.1
  netmask 255.255.255.0

Notes

If you configure your network _before_ following the ltsp-pnp installation steps, then ltsp-config dnsmasq will create an appropriate /etc/dnsmasq.d/ltsp-server-dnsmasq.conf for you. If you do it afterwards, just re-run: ltsp-config dnsmasq --overwrite (but remember to re-disable the "dhcp-range=192.168.3.0,proxy" entry in the freshly generated /etc/dnsmasq.d/ltsp-server-dnsmasq.conf