IS RHEL 4 AS configured as router and working from XP?


Code:
LAN - RHEL - Router


I could not understand above statement and code. RHEL server act as a router. Clients are Winxps

Also i installed squid in the same RHEL and it is working fine. Squid I am using for blocking site and i allow internet for particular ip.That is working fine

If people are under squid for them,I gave only ip and subnet in the network settings and in the browser Tools -> Internet option -> connections -> Lan setting -> proxy server -> tick use proxy server and gave the ip address of RHEL and port address 3128. It is working fine

Problem here is , If I remove tick from use proxy server under Lan settings of the browser and in the network setting If i enter default gateway address i.e RHEL ip and DNS , I can able to browse with all sites with no restriction .

These all I explained in my first mail.

I want to allow internet for two groups

For one group of ips I dont want block any sites , they can browse always. This group i am now using iptable. i.e I filled ip ,subnet,gateway and DNS in the netwrk settings. Because this RHEL is made as a router.

For second group , I want block some sites and they are permitted for browsing some particular time . This group I am using squid in the same RHEL i.e i filled only ip, subnet and did modification in the browser settings

Problem here is that most of the second group people knows the first group setting, They simply untick the use proxy server in the browser setting and they just add gatway address and DNS. Now they can browse always without blocking any sites.

What I want is even if the second group people modify network setting .i.e adding gatway and dns and untick the use proxy, They should not able browse they should browse only what time i allow using squid.

How to make iptable rules that only allow the ips first group .