Hello, I've got a problem with iptables I'm trying to activate nat between
my two networks

eth0 192.168.3.x/24 and eth1 192.168.4.x/24

I already activated ip_forwarding with my /proc/sys/net/ipv4/ip_forward set to 1 and I can ping from one network to the other.

The only rule I added to my iptables is to redirect any incoming tcp connection on 192.168.4.30 (that's my router eth1 interface address) on port 1521 to 192.168.3.23:1521 (a client computer from my 192.168.3.x network).

iptables -A PREROUTING -t nat -p tcp -d 192.168.4.30 --dport 1521 -j DNAT --to 192.168.3.23:1521

But that rule is not working.
when i try to connect on port 192.168.4.30:1521 the connection is not redircted to 192.168.3.23:1521
but if I try to connect directly to 192.168.3.23:1521 it works bu there is no address translation.

Ipchains is not installed.
my iptables version is 1.3.5
my debian kernel version is 2.6.17.10

Thank you.