Sharing dialup connection over network cable

[s y]

As a new Ubuntu, so to say, Debian user, I am not too
much familiar with the structure. But some times ago,
while I was trying to build up a small net which can
establish a connection via modem, by using a red-hat
installed machine to which a Windows loaded one has
been connected, I've used several mini-howto documents
written for red-hat. These really worked and helped me
too much. I'm not so sure if these work with Debian
but main topology for this net that worked fine in my
flat was something like that:

ppp-modem --> Linux-Box---> windows(or another linux) 
[A]       [B]    [C]   [D]  [E and possibly others]


[A] can be an isdn, adsl or whatever you use for
dialup connection (can be another option which
connects you via ppp). But if you get it as a main
connection for your ISP, it's clear that you don't
need to worry about type of the cable. If it works
that it means everything is fine for you.

[B] it depends to your modem. Can be a serial port at
the other end and connects it to your computer; or an
ethernet cable which connects your modem to computer. 

I suppose, any case it is delivered with your
hardware. If your modem is an internal one you need to
split your phone line, that I suppose you can do it. I
can't give alot about thecnical spects but I'm sure in
this list there're too many person can give  details
about these.

[C] This part of work needs some effort :) I'm really
sorry because that I can't give you details one by one
because I don't really remember most of. But I can
recommend you to check internet especially for pppd,
which is once used (is it used nowadays???) as a point
to point connection protocol daemon with its own *-up
and *-down (these are starter and termination script
files for this daemon) script files. 

Beside these you need to care about your sub-net which
means the computers that you want to connect to
Internet by using your ppp connection [A] and via the
one [C] which has this connection. 

If you don't want to use [C] as a domain name server
(it necessiates extra effort to learn about DNS
configuration but useless if you have 1 or 2 computers
connected to [C], or ,  you have a dsl modem -means
you can configure it at least as a bridge and directs
your requests to ISP's DNS-) it's enough to configure
your "hosts.*" and resolv.conf files according to your
sub-net IP's and your ISP's DNS IP's. 

These are main points that I can tell because I'm new
in DEBIAN and UBUNTU. But I think these points are
same for all distribution as they all come from the
same vein. Anyway, you can browse for "Home
networking" mini-howto, "networking-howto" and
"ppp(d)-howto" which can be good references for
details (and if you decide to use your [C] as a DNS).

And your main point;
[D] the cable that you need to use

If you have ethernet cards connected to your [C] and
[E and others] it should be an ethernet cable in CAT
category. As far as I know the biggest problem is
crossing the cable connection while you're connecting
your computers directly to each other by using
ethernet. Also if you have an old fashion dsl modem
which can't recognise one to one connection or a hub
in same type, it should be the case (!!!!! yes, hub is
exactly another point, so another option for you. you
can add a hub to your system which can help you to
connect your [C] and [E] to the ppp-modem -if it's an
dsl one or, if exists one which can accept packages
from different ip's, but surely it means that you need
another topology which has a DNS between this hub and
ppp-modem, or if you have more than one computer in
your sub-net then to connect [E] and others to [C]). 

Ok, back to crossing the cable issue: it means you
need a cross-cable (it's called cross because you
can't directly connect cables in CAT standart to the
same pins at each end, and, you need to connect them
in a crossed manner. But I think it's not a monster
issue to understand why. Possibly all related with 
1's and 0's, means there exist a signal and there's
not). You can easily find the right reciepe in
internet. Also you can find some smart guys in
computer shop's hardware or technical supp.
departments who can prepare this cable to you in
several minutes.

[E and the others]

You need to configure your computers in your sub-net.
Means you need to use the configured IP's for DNS,
Gateway and their own IP's that you assign to them,
and Netmask. While you're doing so you need to be
carefull to use the assigned blockss of IP addresses
for local network. Otherwise you can really disturb
and be blocked up (not only your net but possibly
others too) in Internet. I can recommend you to check
out IPV4 rfc's, "networking how-to"s and if you use
IPV6 same references (I mean rfc's too).

So, what's more? You can consider to use DHCP option
which is usually default one while you're installing
your Linux distribution. It sounds like to be more
comfortable and effortless, but, you need to look
around for configuring DHCP server -if it's not your
dsl modem, most possibly it takes it's IP from your
ISP in a Dynamic way and you can configure it for your
sub-net either as a DNS or a DHCP which can resolve
static IP's requests and also, if you configure it as
a DHCP, assign an available IP to  clients in your
sub-net. 

If you prefer to configure it as a DHCP it's better to
care about your hosts.* and resolv.conf files as these
are for static IP assignments. I think yu can write a
script which can possibly change their lines in a
dynamic manner at startup (honestly, it's just a
guess, I didn't try it before :) ).

I hope these can help you. Just a last word, everytime
I try to do something in Linux, I find myself in
between the feeling of giving up and giving necessary
effort to crawl under a lot of pages around internet
and "how-to"s. Guess what do I usually prefer :) 

Don't get me wrong, I just try to say if these that I
wrote (I can say there is more than these in
"how-to"s) and the possible other recommendations seem
too much for you to handle, just think who can learn a
lot from your experiences in case you don't give up ;)

Cheers,

PS: http:\\www.tldp.org can be a good reference ..



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