Ports and NAT

This main section holds a big part of the key to understanding how a home router works and what it does. The information is a little bit more advanced than what’s in the basic section. The main theme is focused on how Ports and NAT (also known as Address Translation) function. To understand these topics and why NAT is used we must also first look at a few other subjects.

Knowing more about how ports work paves the way to understanding how a router lets multiple computers on the inside LAN share an IP address on the outside by using address translation or NAT.

Areas that are brought up within this section include the following:

• Public and Private IP addresses. Knowing the difference and why the two exist lets us understand the basis for why Address Translation is necessary
• What ports and transport protocols are, which is one of the keys to understanding how a router performs NAT
• NAT, one of the main focus areas of the section
• What the UDP and TCP protocols are, and how they are different from each other. As you will notice it is impossible to separate Ports from these two protocols.
• Why Port Forwards are sometimes required in a router, a subject that cannot be discussed without first learning about the other topics above

After reading through this section, you could also move on to the specialisation subjects on Ports and NAT. There you can gain a more advanced understanding of how address translations work and what roles that ports have in network communication. To avoid bringing up too many things at once, we have moved those more technical explanations to the specialisation section in the main menu.