How to access a PC connected to a router from an external network?

Question

Computer networks

This may be a dumb question, but I'm only versed in networking.
There is a PC under Ubuntu, the SSH port - 22 is open, the PC is connected to the router, how to access the PC from the external network if the router is using the external IP. From the inside, using the internal IP, the SSH connection works.
How to connect then, do you need another way, or should the format of accessing the PC over the network be different?

Answer 1

If the router has a white address, you need to forward any free port to port 22 of the local car and knock outside <router address>:<forwarded port>