Why won't a 3G router do port forwarding when on the 3G interface?

I noticed my TP-Link MR3220 3G/WiFi Router port forwarding will only work when I use the WAN port and not the 3G connection (modem).

Technically the router offers an option to use the Internet from 3G, WAN or both (given a priority). In my case I am only using 3G and apparently, the router features such as remote management and port forwarding don't work on this interface.

Can anyone confirm this? If so, is there any workaround (static routing or something)?

Solution 1:

Even though you get a real IP (which you can ping from any computer on the internet), it won't be possible to forward incoming connections.

Apparently all Mobile Internet Service Providers (ISP) block any kind of incoming connections. So, no matter which port I want to forward it will be blocked by the ISP. (connection requests will never reach the router).

Solution 2:

Many 3G service providers do not allow you to host servers on their connection. The problem in the case above is not the router but the 3G connection.

In Malaysia of the 3G service providers only MAXIS (ISP) allows incoming connections (hosting servers) the rest do not allow it.

Solution 3:

With the TP-Link MR3220 I was able to port forward on a Verizon 4G device (with a static IP). On the router you need to change the remote management interface port to a port other than a port you're trying to forward. So if you're trying to forward port 80 you need to change the remote management interface to another port, like 81.

Solution 4:

All the 3G usb modems connect to a PPP server and it obtains its own IP address from the PPP server. The IP assigned to your TP-Link modem it the local IP provided by the USB modem. So even we have a unique public IP we cannot forward the incoming connections as we are not able to configure the USB modem.