routing/gateway issue

I'm setting up a linux box with Red Hat 9. I have DSL so I want to
setup a firewall and run an internal network.

The external nic gets an ip from my router.

The internal nic has a static ip 192.168.1.1. From the Linux box I
can get to the internet without a problem.

On the internal nic I setup DHCP. I connected my laptop to the
internal nic with a crossover cables. It appears to be working. I
get all the necessary information that I need. From the laptop, I can
ping the Linux box, both nics. But I can not get to the internet. So
while my internal network is working great, I need to get to the
internet.

Is there somewhere in the network configuration that I need to
identify the gateway? I'm missing something, but I don't know what.
Any ideas/suggestions would be great.

Thanks,

Rachel

On 18 Nov 2003 14:45:58 -0800, Rachel McPhail <(E-Mail Removed)> wrote:
> I'm setting up a linux box with Red Hat 9. I have DSL so I want to
> setup a firewall and run an internal network.
>
> The external nic gets an ip from my router.

Is the external nic to a multiport router, or just a dsl modem? Is your
your external Linux nic a private IP (what range)?

> The internal nic has a static ip 192.168.1.1. From the Linux box I
> can get to the internet without a problem.
>
> On the internal nic I setup DHCP. I connected my laptop to the
> internal nic with a crossover cables. It appears to be working. I
> get all the necessary information that I need. From the laptop, I can
> ping the Linux box, both nics. But I can not get to the internet. So
> while my internal network is working great, I need to get to the
> internet.
>
> Is there somewhere in the network configuration that I need to
> identify the gateway? I'm missing something, but I don't know what.
> Any ideas/suggestions would be great.

The laptop needs a gateway to the internal nic of the Linux router, and
the Linux router needs ip_forward enabled. But the dsl router
probably knows nothing about your internal network behind the Linux box,
so you either need to enable masquerading on the Linux box, or something a
bit more difficult to explain using different netmasking and proxy_arp so
everything behind your dsl router ends up within the 255.255.255.0 network
it is expecting on its LAN.

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