On 9 Sep, 21:30, John Rivers <firs...@btinternet.com> wrote:
> Given three Ethernet devices:
>
> PC A (Win XP)
> PC B (Win XP)
> Cable Modem (actually ethernet bridge)
>
> All connected to an Ethernet Switch
>
> PC A uses DHCP to get public IP address via Cable Modem
>
> Internet connection is working perfectly
>
> the problem is the ISP will only allocate one IP address per cable
> modem
>
> so when PC B sends DHCP request it is refused
>
> all the software NAT solutions expect two interfaces
>
> but my "public" and "private" networks are both on PC A Ethernet
> Interface but on different subnets
>
> (using registry hack PC A and B both support DHCP *and* static
> 192.168.1/24 addresses)
>
> what I need is a software NAT on PC A that will accept IP traffic from
> 192.168.1 subnet and NAT out to public network
>
> I could just buy a cable router and junk the cable modem
>
> but am now curious if this is possible

You need to configure your PC B to have PC A as a gateway for ALL
addresses - then configure your PC A to act like a router. But, in
this configuration I do not think that firewall function of this PC A
router will be useful. Because your cable modem (and everybody
outside) will still see your PC B and will be able to access it if you
are not careful in configuring firewall on PC B.