Hello, I'm currently attempting to port forward port 25565 to set up my Minecraft server running on a Raspberry Pi 3 Model B+, but no matter what I do, port checker tools such as canyouseeme.org always report the port as closed, and I've confirmed that external connections can't resolve the hostname of the server.
My setup is as follows, a Nokia G-240W-F router/modem provided by my ISP connected to the internet, which in turn is connected to the WAN port of a D-Link DIR-615 T1 router. My Pi is connected by LAN on port 2 of the Nokia router, which is on route mode (port 3 doesn't work, it's on bridge mode and I can't change it).
The firewall is disabled on both routers, and UPnP is enabled on both.
I've tried connecting the server to the D-Link router and port forwarding on both routers, but that also didn't work.
I called my ISP, they said that they don't block any ports and that I'd have to call my own specialist to resolve my issue (I also confirmed that I have a dynamic IP, so I configured DDNS with no-ip).
1. Nokia G-240W-F is portforwarded external port 25565 to internal 25565 on the IP of the D-Link router
2. D-Link router is portforwarded external port 25565 to internal 25565 to the IP of your RPi
3. DDNS is configured on G-240W-F router, or some other computer in your LAN
Is that correct? Also why double NAT inside the house? Is there a reason to leave the D-Link in router mode? Are you able to disable routing and just turn the D-Link into an access point (no NAT on the d-link, just let it pass data from the G-240W-F)
Also double check your config file to ensure there is not a 2nd port that requires forwarding. That was my issue. I had 25565 open, but my config also had a 2nd port that required access for WAN users.