NAT Address Translation, Concepts, and Principles of Operation

In this session, we're going to talk about address translation NAT in the network.

 

 

1. NAT (Network Address Transloation)

 

 

A system that converts one IP Address (public, external) into one or more IP Addresses for a specific purpose.

 

The private IP band used internally must be changed to a public IP address in order to enable the Internet.

 

 

Why?

 

Private IP Address: Home-to-home address (Michael's master bedroom/Michael's living room/Michael's bathroom, etc.)

Public IP Address: Unique home address (No. 1101 on the 11th floor of Gil-dong Building, Guro-gu, Seoul)

 

 

 

If we don't have a home address when we send a letter, we can't receive it. The home address should be the only address in the world.

 

The same goes for the Internet, but private IP, as explained above, is anyone's home address? It is explained in the master bedroom/living room/kitchen, etc.

 

 

If you send a letter with the address that this gildong is the master bedroom, of course you can't get a reply to the letter. Why?

 

If the destination is Michael's master bedroom, the postman will be surprised and wonder where to put the letter... that's the difference between private and authorized IP Addresses.

 

 

As shown above, in order for a private IP band called 192.168.0.X to become Internet, it is possible to change to an authorized IP called 211.204.12.1 through an equipment firewall that can provide NAT in the middle and attach the address to the Internet.

 

 

Usually, the firewall does a lot of the equipment that can be NATed. This is because it is configured as a private band below the authorized band above the firewall.

 

However, L3 and higher equipment can support NAT capabilities, so you can set up NAT if you really need it on your router or backbone switch.

 

 

Of course, NAT functionality is also available on L4 switches. NAT is largely divided into internal > external / external > internal.

 

Inside> Outside: It means changing the IP Address of the origin when going from inside to outside. It is called SNAT (Source NAT).

 

External> Internal: It means changing the destination IP Address when going out from the outside to the inside. It is called Destination NAT (DNAT).

 

 

 

2. Two reasons for using NAT

 

 

- The advantage of using private IP is that public IP can be saved because public IP is not infinite.

 

- The advantage of being protected from the outside by using private IP is strong in security.

 

Let's remember one thing! The Internet address is the same as my home address. There's no one in the world.

 

So, when you send a letter, you can get a reply. Private IP is used by a lot of people around the world at the same address, so you can't use it for the entire world.

 

a unique address The fact that an Public IP address is essential for the Internet, and for that, it uses NAT technology to change private IP to public IP.

 

Private/Public IP Addresses that you use First, check the private IP Addresses to make sure that they are NATed.

 

 

If you type ipconfig in the Dos window, you will see the IP you are currently using. I am using a private IP Address called 192.168.219.102

 

Second, type ipconfig.co.kr in the Internet window.

 

 

 

You see the address in red called ip address.

That is the authorized IP Address currently used.

 

I use the address 192.168.219.102 internally, but when you use the Internet, you can verify that you are using the Internet by NATing with the authorized IP Address 112.152.97.1xx through your router at home.

 

Check it out at home. It'll be easier to understand.

 

 

 

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