I have create these 2 rules to allow remote desktop connection to one of the windows 2008 server.
I checked on the local network if RDP is working and I also checked if on my laptop the firewall is turned off.
On the server 2008 I verified if port 3389 is used (just in case),
I can connect with RDP to this server when I am on the same subnet, but when using a vpn connection, I am not able to connect with rdp,
I can ping the server, but RDP is not working

here are the rules I used:

iptables -A FORWARD -j ACCEPT -p tcp --dport 3389
iptables -t nat -D PREROUTING -p tcp --dport 3389 -j DNAT --to-destination