Enable NATting for internet connection:
ppp0-internet connected port
add on startup or to /etc/init.d/rc.local
sudo iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE
Enable Packet accep for incoming requests:
Edit following file and change/uncomment following line to enable packet forwarding for incoming request packets.
/etc/sysctl.conf: net.ipv4.ip_forward = 1
to get control over the packet forwarding, we can forward all NATed packets to a local proxy server
to disable direct packet forwarding, change
/etc/sysctl.conf: net.ipv4.ip_forward = 0
then add an additional route;
i don't know whether the sequence of following will affect, just check you guys ans let me know....
iptables -t nat -A PREROUTING -i eth1 -p tcp --dport 80 -j REDIRECT --to-port 3128
iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE