DNAT problem

[Antonio Di Bacco <antonio.dibacco@xxxxxxxx>]

I receive on an interface (eth0, NOARP , ipaddr: 192.168.0.20 ) a tcp packet 
in this way (I have dumped it with tcpdump):

SRC: 192.168.0.21:6000 
DST: 192.168.0.21:80

I have an iptables rule:

iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j DNAT 
--to-destination 192.168.0.20:80

Why my web server listening on eth0 doesn't receive it?

Thank you,
Antonio.