[K12OSN] Networking configuration

John Lucas mrjohnlucas at gmail.com
Mon Jun 16 23:44:32 UTC 2008

Jeremy Schubert wrote:
> I used to have three clients connected to by dlink device that acts as a 
> switch, dhcp server and proxy server (shares the internet, but I guess 
> not exactly a proxy server, anyway...)  Client computers gateway is set 
> to the ip of the dlink device.   The dlink device is connected to the 
> cable modem.
> Now I have introduced my CentOS ltsp server.  Currently I have eth0 and 
> eth1 plugged into the dlink device.
> So, do I have to plug eth0 into my cable modem and eth1 into my switch?  
> And then the gateway for my client computers would be the ltsp server 
> instead of the dlink device? 

You shouldn't have both NICs on the same network segment (subnet), it 
will not work.

As I recall the client side of LTSP is on eth0 by default, so eth1 would 
go on the cable modem and eth0 goes on the LAN side (not WAN side) of 
the Dlink. Your clients also go on the LAN side of the DLink. This 
assumes you want to use the LTSP server as your router/firewall instead 
of the DLink. If this is the case, then be sure to *turn off* DHCP on 
the DLink and let the LTSP server handle that task too. The WAN side of 
the DLink will not be used. The client's default route would point to 
the LTSP server (be sure to turn on packet forwarding if you have PCs 
that need to pass traffic through the server).

The other way to do this is to run a single NIC LTSP server (only eth0) 
and plug the LTSP server and all clients onto the DLink LAN side, turn 
off DHCP on the DLink but continue to use the DLink as your 
router/firewall with the WAN side connected to the cable modem. In this 
scenario, the DLink would be the default route for all clients 
(including the LTSP server).

> Also, during the ltsp install, the eth0 was designated x.x.x.254 and 
> eth1 dhcp.  Currently I connect to the server using putty (ssh).  Is 
> there a cmd line I can use to change the eth1 to static and modify both 
> cards address?

You can usually change the network configuration with a GUI too. I use 
KDE and installed the KDE admin tools, which adds an "Administration" 
item to the main menu. The exact setup depends on your ISP. The single 
NIC setup wouldn't require changing eth1, because there would be no eth1.

         "History doesn't repeat itself; at best it rhymes."
                         - Mark Twain

| John Lucas                MrJohnLucas at gmail.com               |
| St. Thomas, VI 00802      http://mrjohnlucas.googlepages.com/ |
| 18.3°N, 65°W              AST (UTC-4)                         |

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