Hi List

I have a Linux box that allows LAN users with local IP addresses to access Internet using the following IPtables based shell script. I have basic understanding of IPtables and have done some reading on how to fwd all dport 80 traffic to a separate box that runs a caching server (Squid in my case). Can someone help me with changes in the existing setup:

--> to forward all the traffic to the squid port (say 8080) on a separate box or;

-->to a local port (say 4000) running transproxy that simply forwards all the requests coming to local:4000 on to the squid box at port 8080.

#!/bin/sh

# Set up default policies
iptables -P INPUT ACCEPT
iptables -P OUTPUT ACCEPT
iptables -P FORWARD DROP

# Flush all tables
iptables -F
iptables -t nat -F
iptables -t mangle -F

#NAT
iptables -t nat -A POSTROUTING -o eth0 -s 192.168.1.0/24 -j SNAT --to-source 202.xx.xxx.xx

# Forward all traffic for Local Network
iptables -t filter -A FORWARD -s 192.168.1.0/24 -j ACCEPT
iptables -t filter -A FORWARD -d 192.168.1.0/24 -j ACCEPT

# Enable IP forwarding.
echo "1" > /proc/sys/net/ipv4/ip_forward

Also, please guide me to some good document on IPtables.

Thanks in advance

Charan