Re: Routing public IP's through a gateway

Tim Groeneveld <tim@xxxxxxx> · Mon, 15 Oct 2007 22:14:44 +1000

On Sunday 14 October 2007 11:07:10 pm Tim Groeneveld wrote:
> Greeting all,
>
> I have a bit of a complicated question.
>
> I have two ethernet devices, eth1 and eth2.
>
> eth1 is where my internet comes from. It is in the form of
> 202.172.122.208/29. It has another IP range, 202.172.122.72/29. What I want
> to be able to do is route 202.172.122.72/29 to eth2, so that other machines
> can use those IPs, any ideas on how to do this, I cannot work out how to do
> this.
>
> eth2 has a DHCP server, which only gives out IPs 202.172.122.74 to
> 202.172.122.76.
>
> eth1 is basically just hooked into my internet router, while eth2 is hooked
> into a switch, and will be used for other computers.
>
> If anyone could help me with this setup, I would more then appreciate it.
>
> Thank you very much,
>
>      - Tim Groeneveld
>

To extend what I have tried to say further:

My ISP has given me two IP ranges. 202.172.122.208/29 and 202.172.122.72/29. 
They are unable to give me any larger IP ranges for some lame excuse, which I 
am sure was written by the BOfH.

Does your isp route 202.172.122.72/29 to me? Why yes it does. It routes this 
IP through the gateway 202.172.122.209.

If I want to give a machine an IP in 202.172.122.72/29, this is what I need
   > A machine already in the 202.172.122.208/29 IP range.
   > ip route add 202.172.122.72/29 via 202.172.122.209 dev eth1
   > ifconfig eth1 202.172.122.73 netmask 255.255.255.248
(where on this machine, eth1 is hooked into my router).

What I would like, is a gateway machine, which will use eth2 to provide a 
gateway for other machines to assign themselves .72/29 IP's, *without* the 
need of 202.172.122.209 being in the route table.

So, there would be *one* gateway machine. This gateway machine has (already) 
an IP on both ranges.
    > 202.172.122.211 (eth1)
    > 202.172.122.74 (eth2)

eth2 would then be connected into a switch, and eth1 into the internet router.

I am not sure if this helps at all, sorry if it does not.

Thanks again,
     - Tim G