RE: IP forwarding / IP Masquerade

From: Dirk Heilemann (
Date: Fri May 31 2002 - 13:41:16 CEST

> I have been trying to connect 2 PC's via a LAN (succesfully) to a mulinux
> box using static IP addresses and everything (Telnet/VNC/Web/FTP) all
> works fine. I can also connect to an ISP using a Modem PPP connection no
> problem with the Mulinux box.
Isn't (mu)Linux great?

> However, I am struggling with IP formarding. If I get an IP address for
> the Mulinux box over DHCP from the service provider how do the other
> machines on the LAN know what this IP adress is. Or is it the case that
> the Mulinux box has two addresses, one for its LAN connection (static) and
> the other for the PPP to the ISP (Dynamic).
The "official" IP you get from your provider is bound to the serial
interface. Don't care about it, because it changes every time you dial.

Now put a "private" Address eg. on eth0 - the one that's
connected to your local PC or a hub. Configure an address from the range to for all local devices and enter as the default gateway.
btw.: /24 =

With the "masquerading" feature of linux your PCs will use the official IP
through the internet. With this setup you will be able to do most of the
thing you need except running your own servers. "IP (Port) Forwarding" is a
bit more complicated. Come back later then... :-)

> Any advice would be very gratefuly received, I have nearly a very
> functional system here, and would love to get it working correctly.
> Many thanks to all
> Adrian
You are welcome,


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