Yeah, the Windows Defender Firewall with Advanced Securit...

[Kiesmander]

Yeah, the Windows Defender Firewall with Advanced Security, I know. And yes, the IP and the port are valid and correct. I will say it AGAIN. Port Forwarding worked perfectly fine until I was given the XB6 Bluecurve modem.

[mdk]

@Kiesmander -- after adding the port-forwarding rule on your XB6, did you disconnect the electrical power cable for a few seconds, then reconnect the cable, to force the XB6 to do a complete restart, which hopefully will "apply" the rule.

Also, if the Ethernet connection on your target computer has a lamp that blinks whenever it sends/receive traffic, does it blink at the same moment that you try to connect from your "external" device, to show that the traffic is reaching the Ethernet adapter (before Windows can do anything, such as "drop" the packet). Can you send packets at the rate of 1 per second, and see matching "blinks" at the same rate?

Within Windows, TCP/IP packets can be traced:

C:\> netsh trace ?

The following commands are available:

Commands in this context:
? - Displays a list of commands.
convert - Converts a trace file to an HTML report.
correlate - Normalizes or filters a trace file to a new output file.
diagnose - Start a diagnose session.
dump - Displays a configuration script.
help - Displays a list of commands.
show - List interfaces, providers and tracing state.

start - Starts tracing.
stop - Stops tracing.

To view help for a command, type the command, followed by a space, and then
type ?.

[Corbio]

So I've read your post and the replies and from what I've gathered thus far, it's either the application (minecraft server) isn't running on the port you are port forwarding or at the very least, isn't defined in the server setup properly for that running instance (taken into account that you selected the correct LAN device). You could use a port checker website so as long as you are using the appropriate protocol for checking TCP and UDP ports as "OPEN" (various sites handle different protocol port checking). Just remember that port forwarding will only display as OPEN on those sites IF the application that uses it, is actually running with it at the time of checking.

I run bridged mode on my XB6 and have a dual router setup (merlin firmware) with one acting as a switch (DHCP disabled on it). It is normal for the Gateway (XB6) to have a different WAN IP address when in bridged mode, while also using a 3rd party router for DHCP routing; this router will also have it's own WAN IP address alongside the ISP Gateway's WAN IP address. Some context, the Bridge mode mentioned with the older Hitron model Gateways, do in fact, function differently than the now outdated Arris/Technicolor Gateways (XB6) and it's because of BlueCurve not supporting IP Passthrough function when Bridge mode is enabled. This is also carried over with the newer XB7 and XB8 models too; it's not just for ISP remote managing the Gateway either.

What you need to be checking, is make sure your router is using up-to-date firmware first. You've already checked that the Gateway does not have any connected devices. That's a plus! So everything connected will likely being routed from your TP-Link AC1750. Every router behaves differently when port forwarding is enabled. Some require router rebooting after creating the port profile (most do not), some require internal port assignment and not only just the external while in the profile. That the associated LAN device IP that is being used for the port forwarding that you've selected, hasn't changed in address or in some cases, did not update properly in the port profile if it did. You will want to confirm this!

In case you are as I can't read minds, you do not connect to your Minecraft server using the ISP Gateway WAN IP (or give out this IP for friends to use to join). You only use the WAN IP assigned to your router which you can view on the router's admin page or on a whatismyip website. That is the only one you use for connecting to your server (which you will want to join locally and not globally anyway - just you) and regarding the Gateway, there is no need to go into the admin page for it anymore. Once Bridge mode is enabled, forget about the Gateway completely. I believe this is where the problem or hang-up is happening here.

Perhaps a solution will arise after reading all of this if nothing else helps.

Cheers!

[Kiesmander]

After all of this back and forth, I turned off and turned back on bridge mode on my XB6 and power cycled it (for the FOURTH TIME) and this time it is finally working. I have ZERO idea what the XB6 was doing that was blocking ports but now it's working.