Re: Hi, having trouble with networking

From: Tauno Voipio (
Date: 11/14/04

Date: Sun, 14 Nov 2004 16:02:56 GMT

Mmm_moo_cows wrote:
> Hello,
> Sorry if this is a well worn topic, but been searching out there for
> the past week and I'm getting nowhere,dont want to go back to windows
> XP!
> Could anyone reccomend a good (basic) networking tutorial for a
> beginner in linux. I have setup modem and internet, but would like to
> share internet to 4 windows XP pc's and I amd completely stuck and
> tutorials on the web I have found just dont help.
> In a bit more detail,
> New to linux and having a bit of trouble networking. I'm in a student
> house, 4pc's running win xp and a server pc. This server pc was
> sharing the internet connection (adsl) and acting as a fileserver.
> However, with windows XP I'm having to reinstall it every month
> becuase it just slows down after a bit then crashes all the time (no
> idea why) which is why I want to change it to a unix/linux server.
> So, bought redhat (not too sure which version, a new one maybe 9 (has
> iptables)). Managed to install it fine. Got some drivers for my
> modem (bt voyager -EciADSL drivers from
> and got all that setup, so I now have the internet installed and
> working.
> My trouble lies in basic networking and sharing the internet
> connection. My network car has been recognised by redhat and it seems
> to be installed.
> I ran netconfig from the console and assigned it adresses
> with matching gateway etc address (it filled it in one the main ip was
> entered).
> however, I cannot seem to ping it from my windows xp machine (I thinlk
> I havent set it up correctly).
> So here comes my real problem. Searchin on the internt, news groups
> and tutorials found a handful of tutorials, but all are different and
> all have not helped me.
> So, could anyone recommed any good tutorials, or even better help us
> in the right direction.
> Not to sure also about the windows configuration side, but every time
> I utter the word windows in a search on google I get so many unrelated
> pages.
> Thanks for any help.
> Jon

Networking tutorials:

Have you waded through the HOWTO documents in the Linux Documentation
Project (<>)?

The Networking-Overview-HOWTO is a good starting point.

For a deeper understanding of the TCP/IP networking, my favourites
are the books by the late W. Richard Stevens (google for the name).
Be warned: there are thousands of pages to read.

Your server:

You are pretty well off if the router computer sees the connection
to the ISP.

You need two netrwork interfaces in the computer: one for the
outward Net and the other for the internal shared network.

The outward net IP address and netmask come from the ISP, either
by DHCP or statically assigned.

The internal network should be picked from the RFC 1918 networks:

   10 0.0.0 to
  172. 16.0.0 to 172. 31.255.255 to

Some ISP's like to use also one of these, usually the 10.x.y.z.
If this is the case, please pick another. 192.168.123.x is often
safe to use.

To access the outside world, you need two things in the router:
  - forward packets between internal and external nets,
  - translate internal addresses so they are acceptable
    in the outside network.

The first thing is achieved by enabling forwarding in the router.

The second thing is called IP masquerading or source NAT. The Linux
iptables handler is able to do it.

There is a third thing needed: firewalling the Microsoft computers,
so that the external network cannot initiate connections, to keep
all binary active contents (worms, viruses & co) out.

There is a series of HOWTOs
about the set-up of iptables.

For file service with Windows units, Linux has to learn
Microsoftese. The package is called Samba. There are also
good HOWTOs how to use it.


Tauno Voipio
tauno voipio (at) iki fi