[ubuntu-uk] [OT] Basic network gateway server setup

[Grant Sewell]

On Tue, 31 Aug 2010 22:58:13 +0100
Eddie B wrote:

> Hi everyone
> 
> Sorry this isn't the right place to ask this... but I've spent the
> whole day reading articles about how to setup networks and routing
> tables and such like and still failing miserably. I'm hoping there's
> something I'm missing that is a beginner's error!
> 
> I'm trying to do something that is probably really simple. I have a
> server which has two interfaces. eth0 obtains an IP (192.168.1.20) by
> DHCP for the internet from a router sitting on 192.168.1.1. The
> server, as such, is able to get onto the internet. eth1 connects into
> a hub, via which all other workstations will connect. eth1 has a
> static IP, 192.168.2.1.
> 
> So far I've got the workstations obtaining correct IP addresses (pool
> starting 192.168.2.100), so I assume the DHCP server is working
> properly, but no more than that. Can't even ping the server at
> 192.168.2.1 - “Reply from 192.168.2.1: Destination host unreachable”.
> 
> My hunch is that it's something to do with the routing tables, or
> maybe the DHCP on eth0, but I can't find a proper answer anywhere on
> Google. I was hoping to find some sort of sample config, as surely
> this is not an uncommon situation, but maybe I'm not searching for the
> right terms.
> 
> For reference, I'm using Karoshi 7, which is based on Ubuntu 10.04
> LTS 64-bit.
> 
> I'm hoping someone here can help. I'm a bit of a newbie to Ubuntu
> networking. If you want, I would be happy to make a donation to a LUG
> or some other FOSS  project in return for your assistance.
> 
> Apologies again for being in the wrong place but I've been a lurker
> for over a year  and didn't know who else to turn to.
> 
> Many thanks
> 
> Eddie

Hi Eddie,

Can I ask what reason you are trying to get all your workstation's
traffic to traverse your server?  I would have thought an easier option
for you, if it meets with your requirements, would be the following:

+ Router has a static IP address of 192.168.1.1
+ Router has DHCP disabled.
+ Server's eth0 has a static IP address of 192.168.1.2
+ Server's eth1 is disconnected and no config applied to it.
+ Server is configured to give out addresses by DHCP with 192.168.1.1 as
the client's default route (and DNS, depending on your setup).
+ Clients then receive their IP address and other network information
  from the server, but all traffic that is not specifically *for* the
  server goes via the Router.

Grant.