My current setup is like this I am running a transparent squid proxy for my internet users. This is the rule that is redirect http traffic to use squid :-

iptables -t nat -A PREROUTING -i eth1 -p tcp --dport 80 -j REDIRECT --to-port 8080

In this case the Linux server is the gateway to all the LAN computers, so when this rule is active a Microsoft VPN client (using pptp port 1194) is failing to connect to the VPN server via internet thru the Linux server. What is happening is that the VPN client traffic is assumed to be internet traffic then is redirected to use squid. I wish to implement iptables that handles VPN client traffic sends it out to the internet.

Here is my diagram :-

Windows Client -------------------------- Linux server--------------------- ADSL Router---------Internet
192.168.1.x eth1 eth0 10.0.0.y
192.168.1.y 10.0.0.x

I will be glad if you can help.