I've got the same problem. Just I'd like to port forward the SMB (445 port). Doesn't work.

There is useful page Open Port Check Tool - Test Port Forwarding on Your Router, (OPCT), where you can check the opened port from internet. It showed that 445 is closed.

I've tried to translate the port as well, from 4445 to 445. OPCT showed 4445 is closed. I've tried these with NFS ports (1058, 2049) as well. Doesn't work.

However, if I tried with RDP (3389), OTCP showed 3389 as opened. Moreover, I did a 4445 => 3389 translation, OPTC showed the port 4445 opened.

So, basically the forward method works.But I guess, that it doesn't work for all port, but just for the ports listed at predefined Application ports. (3389 is there, but 445 or 2049 aren't)

Sure. But the ISP does not block: a Huawei HG8143A5 router (before my current TP-Link router) did forward the 445. Now: 4445 => 445 (SMB): OTCP shows closed 4445 => 1058, 2049 (NFS): OTCP shows closed 4445 => 3389 (RDP): OTCP shows opened So, ISP does not block 4445. If the router forwarded the port 4445 to 445, then OTCP should show port 445 opened

If port forward 4445 => 445 worked on the router, OTCP should show port 4445 opened, independently from the ISP

Thx. So, if I'm right, we agree that TP-Link router blocks 445 port forward in all forwarding rules (445=>445 and 4445=>445 as well), not the ISP. Why does it block??? By default, nothing is forwarded. It is OK.But, if the user wants to forward port 445, then it is the user's responsibility. Why TP-Link blocks user action? Why is it not in the manual? Why doesn't refuse such a forward rule on the configuration page, letting configuring users is doubts???