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Using LINUX as network modem server using SLIP

jlms asked
Last Modified: 2010-03-18

   I was succesful making a connection to my ISP using slip (dip) in my Linux machine, now I want other machines on the network to use this connection to access the Internet, How can I do it? I read somebody mentioning IP forwarding/masquerading but I don't know what this is or how it works.
Any ideas?
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If you want to use a linux box to forward packets from/to the internet, you are creating a gateway. (You should specify
this when compiling the kernel). The gateway configuration
is, as I believe, explained in the net2-howto which you
can find on any sunsite mirror. Now to IP masquerading :
if you only have one IP adress from your provider, you can only
run one computer with it directly. You can have a router (or your linux box) translate your internal ip adresses into the externally valid ones and back.
The configuration of such a gateway-router system requires an
understanding of the underlying principles. I recommend you
look around a bit on the net; e.g. cisco.com has a great website
where many networking topics are explained thoroughly.
(You do _not_ have to buy a cisco router ;-)...)

Hope this helps,


Yes, all what you say sound reasonable, but at least resumed, what are the steps I should follow to connect another machine to the Internet using the Linux box as a router and taking in account I have only SLIP access? Let's say, I have Sun boxes and one SGI machine, how could I make sure users in those machines can use their WWW browsers? If I achieve this, I can do anything else.

Thank you for the help, but I need a little more of information from somebody with hands-on experience.

1. setup your slip dialout scripts (you did that already)
2. configure your kernel to include routing and gatewaying
(using make config) and compile the new kernel
3. install the new kernel with lilo or whatever loader you
4. now comes the net-howto; it explains how to configure
your linux box to route the requests on the internal network
to the outside world
5. configure your clients to use your linux box for ip
as gateway for ip traffic
6. done.
There is nothing special about sun,sgi or whatever - once a machine knows that it can send ip packets over your gateway,
everything is straightforward.
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Your answer is exactly what I needed, now my workstations use the little Linux box to access the Internet.

Thank you and sorry for the delay in grading your answer.
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