[Gllug] How to access the internet

[Bruce Richardson]

On  9 Feb, Raju wrote:
> Bruce,
> 
> I am confused. (Newbie!!)

So were the rest of us.  I don't think anybody got the actual sense of
what you want to do from your first e-mail  .

> 
> I connect to internet thru a dialup account with Freeserve. Can I still make
> the Linux box that is dialing up a "router"?

Yes, the Linux box is the gateway for the other machines.  On the
Windows machines put the ip address of the linux box in as the gateway
in the TCP/IP properties.

> 
> This is what I want to make happen: Whenever anybody on the LAN starts a
> browser and wants a site the Linux box with modem should dialup the account
> and make the connection if it is not already made. This should also work for
> many people on the LAN browsing at the same time.

OK, there's a lot to cover so I'll only sketch the basics.

The connection: you need to set up pppd in demand-dialing mode.  At it's
simplest that means getting ppp to work when run directly from you Linux
box and then running it with "demand" added to the options.

IP forwarding: you need to enable this so that the Linux box will
forward ip packets from other machines out to the internet.  The
configuration tool for whichever distribution you use should allow you
to set this.

IP masquerading: you need this so that several machines can share the
connection and the same IP address.  To the outside world it looks as
if just one machine is connected and your Linux box sorts out the
connections at your end.  Right now the best tool for this is ipchains
- see the IPCHAINS Howto, it has a simple chapter on masquerading.

With two unfamiliar tasks to get right, I would test the IP
masquerading  first.  Just run pppd manually on the Linux box and then
see if you've gotten masquerading right by trying to browse from one of
the Windows boxes.  Once that's working, try getting the auto-dial
feature of pppd working.

You'll probably find that you get pppd dialling out sometimes even when
nobody is browsing.  This can be caused by a variety of things but
mostly by software on the windows boxes pinging something out in the
net.  Some software - ICQ for example, you should just veto cause it'll
keep your connection running all the time.  Other traffic you'll need
to filter out.  ipchains can do that and provide basic fire-wall
capabilities if you want them.

There's a lot to work through if you're not familiar with this.  If you
find you need advice maybe there's a handy guru on the list but it's
not my area of expertise, I've only set it up on my little home
network.  It's probably worth asking for help on one of the linux ngs.

-- 

Bruce

"The good news is that in 1995 we will have a good operating system and 
programming language; the bad news is that they will be Unix and C++." 
- Richard P. Gabriel