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Firewall/Router for Sharing a Cable Modem Connection

A while ago I built a debian firewall from an old 486 which, by virtue
of NAT, my Win98 PC hid behind.  I didn't get as far as using dial on
demand but that was my next step.  I have now moved to an area covered
by cable broadband provided by Blueyonder in the UK.  I am inclined to
sign up for this and rebuild my debian firewall to suit.  I know I could
use something like SmoothWall but like to understand some of what goes
on 'under the bonnet'.  I found building my first firewall a great
introduction to GNU/Linux in general, debian and networking.

If anyone has had any good/bad experiences with this I would be grateful
for them.

Also I have a few queries which I'd be grateful for help with:-

1. The set up will be as follows, I use greek letters for naming
purposes at the moment:-

                                                     / Beta(W98 Desktop)
Internet---Cable Modem---Alpha(Firewall/Router)---Hub- Gamma(Debian
                           |                         \ X Terminals etc
                         Omega (Experimental
                                Web Server) etc

Is it correct to call Alpha a Firewall/Router?  I gather it will get its
external IP address dynamically.  I will use NAT to hide the 10.X.X.X
internal addresses.

2. What packages do I need over and above those I am familiar with for
my old dial-up set-up?  I am thinking mainly of DHCP which I believe is
necessary as I will have a dynamic external IP address.  I think I will
write the iptables rules by hand.  I used ssh in my previous set-up to
login to the firewall internally which worked well so I will do that
agin and make sure telnetd isn't on the machine.

3. Is a 486 up to the task?  I believe the download rate is up to 512K.

4. How can I install Woody with a 2.4 kernel from my CD set?  The
default seems to be a 2.2 kernel.  I don't understand the instructions
on the CDs or those I've found on the internet.  I believe I need 2.4 to
use iptables.

5. I want to get emails generated by Alpha (containing logfiles etc)
delivered via an email address provided by the cable provider *or*
internally.  Am I correct in thinking exim can do both of these
alternatives?  Apologies if I am straying 'off list' here.

6. Does iptables enable the use of things like ICQ and gaming over the
internet 'out of the box' without the workrounds necessary when using



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