The following is adapted from my post
here.
I assume that you've set up your network correctly so that you can successfully ping between your Slackware and Win98 boxes.
Also, I assume that you have only a handful of computers on your LAN, so you are not using DHCP.
I haven't used Windows in some time, so I will try to work from memory. On the Win98 box, you need to tell it to use the Slackware box as the internet gateway. Under Windows networking setup, add the gateway 192.168.xx.xx (192.168.xx.xx is the internal ip address for the Slackware box). Further, under domain name resolvers, add the ip addresses for your ISP DNS servers.
On your Slackware box, you need to edit the /etc/resolv.conf to include the ip addresses for your ISP's DNS servers; the entry in your /etc/resolv.conf is "nameserver 12.23.45.67" where 12.23.45.67 is your ISP's DNS server address.
On the Slackware box, you need to configure iptables to allow IP masquerading and network address translation (NAT) to "share the internet". Assuming that on the Slackware box, the modem interface is "ppp0" and the ethernet interface is "eth0", then copy and paste the following code into /etc/rc.d/rc.firewall:
Code:
# !/bin/sh
IPTABLES='/usr/sbin/iptables'
# load iptables modules
/sbin/modprobe iptable_nat
/sbin/modprobe ip_conntrack
# enable ip forwarding
/bin/echo 1 > /proc/sys/net/ipv4/ip_forward
# flush tables
$IPTABLES -F
$IPTABLES -X
# enable masquerading to allow LAN internet access
$IPTABLES -t nat -A POSTROUTING -o ppp0 -j MASQUERADE
# forward internal LAN traffic from eth0 to ppp0 internet interface
$IPTABLES -A FORWARD -i eth0 -o ppp0 -m state --state NEW,ESTABLISHED -j ACCEPT
# block out internet intrusion on ppp0
$IPTABLES -A INPUT -i ppp0 -m state --state NEW,INVALID -j DROP
$IPTABLES -A FORWARD -i ppp0 -m state --state NEW,INVALID -j DROP
As root, run /etc/rc.d/rc.firewall. On Slackware, /etc/rc.d/rc.firewall is executable by default, but if for some reason it isn't, then chmod +x /etc/rc.d/rc.firewall.
You should now be able to browse the internet from the Win98 box. As a nice bonus, your Slackware box is also a firewall.
DISCLAIMER: I don't use dialup, so I am merely guessing that your modem interface is ppp0. On my rc.firewall script, my internet interface is eth0 (ethernet connected to cable modem) and my internal lan interface is eth1.
