Router ports remain closed!

[Tux1]

Hello,

 

I have a problem and i'm becoming crazy about it. I'm not a native english speaker, so i'm sorry about mistakes.

 

I'm trying to do a "simple" thing: opening a TCP/UDP port on a main router, that is wireless linked to a second router, with a cable to my PC (that come from the second router).

I went into the main router admin page, into "port forwarding", opened the TCP/UDP ports and....they remain closed.

 

The only way to make it works (for 2-3 minutes at least) it's using UPNP on a computer that have ethernet connection to the main router. For a minute, Emule open the ports with UPNP, after closing the wizard, RIP, port closed.

Sometimes (don't ask me why, i have no idea) on the second pc (connected to the second router) UPNP from emule works, but testing the port it result closed.

 

Any suggestion? Some Teamviewer Brave guys? This is a nightmare.

 

Additional infos: My main router is a "Zyxel vmg8823-b50b", the second one is a "Xiaomi mi Wifi Mini router" with Padavan firmware. All routers firewall are completely disabled, Windows one too. I have no antivirus. The image is from the main router admin page. You can check that port online, its closed. The IP next to "emule" in the image, is the IPV4 MAN address of the second router.

 

[mtz_federico]

Is the second router only acting as an access point/switch or is also doing NAT and DHCP?

I think you might be double NATed