How does NAT work? (1)

If you are reading this article, you may already be connected to the Internet. This is a great opportunity for you to use Network Address Translation (NAT! The Internet has grown to be much larger than people had imagined. Although its specific scale is unknown, it is estimated that 0.1 billion hosts and more than 0.35 billion of users are active on the Internet. This is more than the total population in the United States! (This article was published earlier, and now the actual number is far greater than this, the translator) In fact, the Internet continues to expand at a rate of twice a year.

What Should NAT do in the face of the ever-growing Internet? All things! If a computer wants to communicate with other computers or use Web services (such as email and other network services) on the Internet, it must have an IP address. An IP address is a unique 32-bit number that identifies the location of your computer on the network. It is basically the same as your email address: a correct address that can find you and send network information to you.

When the IP address came out, everyone thought that its own address could cover everyone. Theoretically, there are 4,294,967,296 (232) different IP addresses. But in fact, the actual number of available addresses is less than this (between 3.2 billion and 3.3 billion), because the IP address classification method and the need to set up some addresses for broadcast,

With the expansion of the Internet and the increasing number of home networks and corporate networks, the available IP addresses are obviously insufficient. The easiest solution is to redesign the address format to give it more addresses. This solution is under development, but it will take several years to implement, because it needs to replace the global Internet infrastructure.

Which of the following are transmitted from the NAT router to the private network:

This is where NAT (RFC 1631) needs to be saved. In general, Network Address Translation (NAT) allows a single device, such as a router, to act as a proxy between the Internet (Public Network) and LAN (Private Network. This means that for external networks, only a single IP address is required to represent a group of computers (internal networks.

The shortage of IP addresses is only one reason for using NAT. The other two reasons are:

Security

Management

You will know more about how you benefit from NAT, but first, let's take a closer look at what NAT can do...

Knowledge of the reader:

Readers of this document shall have the following knowledge:

Concept of IP address and route

The tool used is described in this document and is not limited by any specific software or hardware.

NAT is like a courier in a big office. Let's assume that you asked the courier to refuse to give you any calls, unless you asked them. Then, you make a call to potential customers (because they are not there) and tell them to return to you. You tell the courier that you are waiting for a call from this customer and allow them to be received.

The customer calls the main number (the external phone number of the office, the translator) to your office. This is the only number that the customer can find. When the customer tells the courier who they want to find, the courier will view a table that matches the company name and the phone extension. The courier knows that you are waiting for the call, so the courier transfers the call to your extension. The Network Address Translation (NAT) device developed by Cisco works between the internal network and the external network. NAT can be implemented in many ways and in many ways:

Static NAT-use a one-to-one device to map an unregistered IP address to a registered IP address. This is especially useful when a device needs to be accessible from external networks. In static NAT, Computers whose IP address is 192.168.32.10 are always converted to 213.18.123.110: