Help with port forwarding

[andresmorago]

Hello guys

I thought this should be easier, but apparently theres something weird here.

My setup is easy:
AC86U running 380.68_4. It has a public IP acquired from cable modem. LAN IP is 10.0.0.1
I currently have 3 opened ports: 80, 9091 and 51414 to a raspberry pi (10.0.0.2) . All ports work well from the outside.

I connected a PLC (10.0.0.200) to the lan side of the asus. This PLC has TCP ports 1200 and 51738 open. I can access these ports from any computer inside my network.
I configured these new ports today on my router so i can access them from the outside but i havent been able to reach these services from a external server that i have. I can access ports 80 and 9091 without issues.

Could you please give me some ideas? Could i be missing something here?

Thanks in advance!



EDIT:
just did some troubleshooting with

 iptables -t nat -L VSERVER -v

the issue is on the servers side which isnt accepting ip addresses different than LAN's

The PLC runs a very old version of WinCE which doesnt allow firewall changes...
do you know if there is any way from asus router to "trick" the plc by changing the incoming connection ip?