Port Forwarding with iptables

[Wilson Mak <wilson.mak@digitalview.com>]

Hi all,

I like to do the portforwarding with iptables(forward web traffic of an 
alias IP - <ext ip> to internal web server).  Here is what I have:

iptables -t nat -A PREROUTING -i eth0 -d <ext ip> -p tcp --dport 80 -j
DNAT --to 10.1.0.12:80
iptables -A INPUT -p tcp -i eth0 -d <ext ip> --dport 80 -m state
--state NEW -j ACCEPT
iptables -A FORWARD -p tcp -i eth0 -o eth1 -d <ext ip> --dport 80 -m
state --state NEW -j ACCEPT

However, it keep droping the packets when getting to the NAT box.

Logs
====
(With iptables -A FORWARD -d 10.1.0.12 -j LOG; iptable -A FORWARD -j DROP)

kernel: IN=eth0 OUT=eth1 SRC=202.xxx.122.xxx DST=10.1.0.12 LEN=48
TOS=0x00 PREC=0x00 TTL=120 ID=6491 DF PROTO=TCP SPT=4023 DPT=80
WINDOW=64240 RES=0x00 SYN URGP=0

Any clues?  Did I miss something here?

Thanks,
Wilson