Proper port forwarding

Question

I try to do port forwarding correctly (under Ubuntu and use Transmission in active mode). Could this be my provider?

I opened port in my Technicolor 7200 router using this guide as follows:

Then, I opened a port via terminal:

sudo ufw allow 6881

sudo ufw status numbered gives:

     To                         Action      From
     --                         ------      ----
[ 1] 6881                       ALLOW IN    Anywhere                  
[ 2] 6881 (v6)                  ALLOW IN    Anywhere (v6)

netstat -lntu outputs:

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 0.0.0.0:6881            0.0.0.0:*               LISTEN     
...................................     
tcp6       0      0 :::6881                 :::*                    LISTEN

But, when I check if port is open using this service, it says:

What I am doing wrong?

Answer 1

While it looks like you have exposed the port to the world, the port will show as closed unless there is a service listening on that port. I suspect that when you did the test your torrent client was either not running or was not interested in communicating with the test website.

Answer 2

Ensure that those ports are actually open on your Linux client:

netstat -lntu

This will output open ports on your Linux machine. Make sure that the ports that you want open are listed and are set to listen. Even if your router forwards those ports correctly, your Linux machine needs to accept that traffic.

Your ISP has assigned you a dynamic IP address which means it can be subject to change, but this will only cause an issue if / when that IP address actually changes. If you want a Static IP address, one that won't change, check with your ISP if they offer them.