Can't figure out how to share internet connection in Red Hat 7.3
 

I just started using Linux about a week ago. I want to share my dial up internet connection, but haven't been able to figure out how to do it. I'm using Red Hat 7.3. Any help would be appreciated.

Hmm...
 

I'm definately going to need LOTS more info....
What's the gateway? Which firewall? Lokkit?
Too many questions to list.....

The linux machine is the gateway, no firewall (at least that I know of, I never set one up on it). I have no idea what Lokkit is. If you could even give me an idea where to go to start configuring the share I coud probably get it working. I just have no idea where to start.

So...
 

You have a modem and an ethernet cart in the gateway?
If so, try the network configuration tool. You'll have devices listed - a modem and eth0. Give the eth0 the IP 192.168.0.1, broadcast 192.168.0.255, netmask 255.255.255.0. The internal computer should (possibly) be setup with IP 192.168.0.2, etc...
That's a place to start....

Also, do this:
/sbin/iptables -L

and post the output back here...

Thanks. I'm trying that right now. I'll post again if I need more help.

Here's the output I got from /sbin/iptables -L

Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

Ouch!!!!!
 

You're running NAKED!!!!!
Better get some clothes on...
Try this: http://iptables.1go.dk
Also this: http://www.netfilter.org/documentati...-tutorial.html
To do connection sharing you'll need ipmasquerade.

Here's a simple script to get you started. This stuff is intimidating at first, but it's really easy. You just need to read and learn.


#!/bin/sh
echo -e "\n\nLoading simple rc.firewall."
IPTABLES=/sbin/iptables
EXTIF="ppp0" #or whatever modem is...
INTIF="eth0"
echo " External Interface: $EXTIF"
echo " Internal Interface: $INTIF"
echo -en " Loading Modules: "
echo " -Verifying all kernel modules are OK"
/sbin/depmod -a
echo "Enabling Forwarding..."
echo "1" > /proc/sys/net/ipv4/ip_forward
echo "1" > /proc/sys/net/ipv4/ip_dynaddr
echo " clearing any existing rules and setting default policy.."
$IPTABLES -P INPUT DROP ##changed from accept
$IPTABLES -F INPUT
$IPTABLES -P OUTPUT DROP ##changed from accept
$IPTABLES -F OUTPUT
$IPTABLES -P FORWARD DROP
$IPTABLES -F FORWARD
$IPTABLES -t nat -F
echo " FWD: Allow all connections OUT and only existing and related ones IN"
$IPTABLES -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT
$IPTABLES -A FORWARD -j LOG
$IPTABLES -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE
#below here is new. above works.
echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_all
echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
$IPTABLES -A FORWARD -s ! 192.168.0.2 -j DROP
$IPTABLES -A INPUT -p ALL -i $INTIF -s 192.168.0.2 -j ACCEPT
$IPTABLES -A INPUT -p ALL -i lo -s 127.0.0.1 -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $INTIF -d 192.168.0.255 -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $EXTIF -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A OUTPUT -p ALL -s 127.0.0.1 -j ACCEPT
$IPTABLES -A OUTPUT -p ALL -o $INTIF -j ACCEPT
$IPTABLES -A OUTPUT -p ALL -o $EXTIF -j ACCEPT
echo " Done loading rules."


Copy this and save it somewhere as: rc.firewall
then as su do: chmod 755 rc.firewall

sh rc.firewall

That should give you some protection temporarily....

Thanks. I'll let you know how it works.