UNIX for Dummies Questions & Answers

Hello, everyone. I have a little favor to ask. Me and my friends decided sharing an ADSL line with four PCs.
PC no.1: Desktop, two netcard (2000 and 8139), Mandrake 9.0
PC no.2: Acer notebook, PC Card, RTL-8139C/8139C+, MS 98 + Win 2000 Pro
PC no.3: Desktop, net card 8139, WindowME + Win 2000 Ads
PC no.4: Desktop, net card 8139, Win 98 + RedHat 8.0
Hub£ºTp-Link 10M
ADSL: eth, no router

Setting:
PC no.1: as server (or router whatever it should be called). connect ADSL to eth0, hub to eth1.
eth0:
ip:192.168.0.1
Mask:255.255.255.0
eth1:
ip:192.168.0.2
Mask£º255.255.255.0
Didn't setup gateway here.
*****************************************
PC no.2
IP£º192.168.0.3
Mask£º255.255.255.0
Gateway£º192.168.0.1
DNS:202.96.134.133
202.96.128.133
192.168.0.1
*****************************************
PC no.3:
IP£º192.168.0.4
Mask£º255.255.255.0
Gateway£º192.168.0.1
DNS:202.96.134.133
202.96.128.133
192.168.0.1

*****************************************
PC no.4:
IP£º192.168.0.5
Mask£º255.255.255.0
Gateway£º192.168.0.1
DNS:202.96.134.133
202.96.128.133
192.168.0.1
*****************************************

I have tried this:
at /etc/rc.d/rc.local
write:
echo 1>/proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -s 192.168.0.0/24 -o ppp0 -j MASQUERADE
...
The firewall choices are:
0 - NONE: This script will not set any firewall rules. You are responsible
for ensuring the security of your machine. You are STRONGLY
recommended to use some kind of firewall rules.
1 - STANDALONE: Appropriate for a basic stand-alone web-surfing workstation
2 - MASQUERADE: Appropriate for a machine acting as an Internet gateway
for a LAN
Choose a type of firewall (0-2): 2
...

The result was: PC no.1 could be connected to the Internet through ADSL and ping other PCs succefully. Others can ping PC no.1 as well but they could go to the Internet. So...

Will somebody tell me what I did wrong and how I should fix it, and why?

Thank you.

Sincererly,

HOUSCOUS

Couple of problems i noticed in your post:

On the machine connected directly to the DSL line, your external interface needs to have a real routable IP address. You should have received this from your ISP (or maybe it is DHCP). It looks like you are using 192.168.0.1 which is a non-routable address.

In your iptables command, you are telling it to masquerade out the ppp0 interface. It doesnt sound like you are using dialup, so you should replace that with eth0 or whatever your external interface is.