A port forwarding rule can be used to redirect traffic to an internal node on the same port that was requested. However, we can also redirect traffic to a different port on the internal node. These are a couple of reasons why we might want to do this:

• Security through obscurity: The port commonly used for HTTP is port 80. We might have a website that we want to make accessible on the public internet, but we want to keep it secret. By setting the destination port range to a different port, we can have an accessible website that is also secret. In this section, we will use this principle to change the external port of the SSH server to make it less hackable.
• Single public IP address: People in environments with only a single IP address may find themselves stuck; for example, they may want to remote access two separate computers using Remote Desktop Protocol (RDP) on port 3389, but there is only a single IP address. By using port redirection, you can set up one port for one computer and another port for the second computer (for example, 51000 and 51001).