Thanks for ur reply that link helped me a little. but the scenario is little different. what am trying to do is am trying to redirect only 3 websites to a particular ip address. and let other all the websites go to internet through DNS. so i need to do string filtering in iptables. i hv tried doing this but always get the following error.
iptables -t nat -A PREROUTING -p tcp --dport 8080 -m string --string "b2e.group.echonet" -j DNAT --to- 172.17.12.1:8080
error i get is :- iptables v1.3.5: STRING match: You must specify `--algo'
Try `iptables -h' or 'iptables --help' for more information.
Advait H. Raut.