Creating a NAT with one eth interface

[Luis Murillo]

I need to create a small network (3 computers) and one of them would
have to be the NAT. Now all 3 machines are hooked up to a switch as well
as the DSL modem. So the network layout would look like this:

	{Switch}
	    |----[MachineA(Ubuntu)]
            |----[MachineB(Ubuntu)]
            |----[MachineC(WinXP)]
            '----{DSLModem}---(Internet)

The DSLModem gives out up to 5 IPs through DHCP. It would be easier to
just have all 3 machines connect to the DSLModem and request an IP, but
only 2 out of the 3 machines are able to actually connect to the
Internet, although the 3 machines get an IP from the DSLModem. So a
solution is to create a NAT, but the "server" or the Machine which has
been designated to do the NATing is installed in a room where there is
only one network cable and it has no more space for a second ethernet
interface. So the NAT would have to be done on one ethernet interface.
I have read that this is possible, but don't exactly know how the NAT is
done. Can anyone help me?

The eth0 on the "server" would have the following set-up:
	eth0 - IP assigned through DHCP (WAN)
	eth0:0 - 192.168.1.1 (LAN)


-- 
Luis Murillo M.
lmurillo at gmx.net
Heredia, Costa Rica

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