LinuxQuestions.org - How to set iptables script for lan

1. give eth1 of computer 1 an ip of 192.168.0.1
2. give eth0 of computer 2 and ip of 192.168.0.2
3. set the default route on computer 2 to point to computer 1

1. #ifconfig eth1 192.168.0.1 netmask 255.255.255.0
2. #ifconfig eth0 192.168.0.2 netmask 255.255.255.0
3. #route add default 192.168.0.1

to get these setting to stick on boot you could later the appropriate
networking script (ifcfg-ethX) in /etc/sysconfig/network-scripts/

Code:

example of my ifcfg-eth0



DEVICE=eth0

BOOTPROTO=static

IPADDR=192.168.1.200

NETMASK=255.255.255.0

ONBOOT=yes

for dns just use the DNS servers that your ISP provides for you or with
RH9 you COULD just turn on named and run a caching only server, it
comes pre-configured with Red Hat.

Code:

open up  /etc/resolv.conf



nameserver 127.0.0.1    <<< use this if you turn on named and only on the machine tired to the net.

nameserver 1.2.3.4    <<< isp provided

nameserver 1.2.3.5  <<< second isp server..make sure you use the proper values

you only have to run 1 DNS server if you really want to run the caching
only name server and that would be the one tied to the internet

for firewalling you'll want the following basic rules (On the computer tied t the internet)

Code:



iptables -P INPUT DROP

iptables -P OUTPUT DROP



iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

iptables -A OUTPUT -m state --state ! INVALID



NAT RULE:



iptables -A POSTROUTING -t nat -s $LAN_COMPUTER -j SNAT --to $INET_IP



or if you have a dynamic ip address you will have to do this instead:



iptables -A POSTROUTING -t nat -s $LAN_COMPUTER -j MASQUERADE



you'll want to add more rules if u plan to run a server on either computer 

because it blocks all INPUT that wasnt established by from you lan or from 

the router itself.

get this stuff working, then consult samba for file and printer sharing, this
stuff is all over these forums also.....try using the search for more help.

i havent proof read this so there may be something wrong, but as i am
an expert :) (kiddin sort of) it should work out fine. i must say that i have
never use RH9 so something may be different about it. I'm giving my answers
based on RH 7.3