Practice
So, the task: forward all traffic arriving on a specific port of our router's external, public IP address to a specific computer inside the local network on a private (internal) IP address - on the same port or a different one.
We'll solve this using iptables - the built-in firewall in Linux.
The following rules will let us forward all TCP traffic arriving on the external interface (public IP) on port 3389 to an internal machine on the same port, and route the traffic back out as well.
Here:
In the previous example, we forwarded the port one-to-one. However, we can do something more clever. For example, TCP traffic arriving on port 11111 of the public IP will be forwarded to port 3389 of the private IP (and back as well). Here's what this example looks like:
The notations are the same.
By the same pattern, forwarding with other variations can be done.
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