How to open a port on an external interface?

Question

linux

Using the command
ssh -v -R extip:8080:192.168.1.100:80 [email protected]
organize port forwarding from extip:8080 (server on the virtual machine) to 192.168.1.100:80 (local com behind NAT)
but for some reason
ssh does not work debug1 responds to the
command: remote forward success for: listen extip:8080, connect 192.168.1.100:80
there is only one external interface
on the server if I look with the command on the server
nmap -p 8080 localhost
from there is an open port
8080/tcp open http-proxy
if I look command on the server
nmap -p 8080 extip
then there is no open port
8080 / tcp closed http-proxy
on an external server with extip there are no restrictions on ports, all ports are open
everywhere ubuntu
what am i doing wrong ?

Answer 1

if I look with the nmap -p 8080 extip command

So where are you looking from the external network? Then it should be open. If from internal - that certainly it will not be opened.