redirection trouble

[Martín <martin@familia-fiumara.com.ar>]

This is the situation:



           Internal LAN machine (192.168.2.5)
                          |
                          |
                          |
(eth1 192.168.2.1) NAT LINUX ( eth0 192.168.1.10 > adsl ppp0 IP dinamic)
                          |
                          |
                          |
             Server 200.45.45.200 (service at port 10000)



This is what I intend to do:
For particular reasons, I need that a soft at 192.168.2.5 comunicate with a 
server with a service at port 10000 (UDP), but this can´t be done through 
normal NAT. So i want to establish a link between both (server and 
192.168.2.5) manually useing the NAT LINUX
So, 192.168.2.5 comunicates to 192.168.2.1 port 10000, the NAT LINUX 
redirect this traffic to the server 200.45.45.200 port 10000. The server 
will respond to the NAT LINUX who will redirect this traffic to 192.168.2.5 
(port 10000 also)
I try to do all this in this way:


iptables -t nat -I PREROUTING 1 -i eth1 -d 192.168.2.1 -p udp --dport 10000 
-j DNAT --to 200.45.45.200

iptables -t nat -I POSTROUTING 1 -o eth0 -p udp --dport 10000 -j SNAT --to 
192.168.2.5


BUT THIS IS NOT WORKING. I GET A MESSAGE FROM THE SOFT AT 192.168.2.5 
TELLING "CONNECTION TIMED OUT"... USEING TCPDUMP i get this as the only 
thing comeing back...:

200.45.45.200.10000 > 168.226.174.184.10000:  udp 8 [tos 0x40]



I would apreciate any help with this trouble
Thanks