Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide


NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

Searchable, convenient, complete TCP/IP information.
The TCP/IP Guide

Custom Search







Table Of Contents  The TCP/IP Guide
 9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)
      9  TCP/IP Internet Layer (OSI Network Layer) Protocols
           9  Internet Protocol (IP/IPv4, IPng/IPv6) and IP-Related Protocols (IP NAT, IPSec, Mobile IP)
                9  IP Network Address Translation (NAT) Protocol

Previous Topic/Section
IP Network Address Translation (NAT) Protocol
Previous Page
Pages in Current Topic/Section
12
3
45
Next Page
IP NAT Address Terminology
Next Topic/Section

IP NAT Overview, Motivation, Advantages and Disadvantages
(Page 3 of 5)

Overview of IP Network Address Translation (NAT)

A very similar technique can be used for connecting an organization's computers to the Internet. In TCP/IP networks, this technology was first formalized in RFC 1631, The IP Network Address Translator (NAT), adopted in May 1994. The word “translator” refers to the device (router) that implements NAT. More commonly, the technology as a whole is called IP Network Address Translation (IP NAT or NAT).

Note: The document status of RFC 1631 is “informational”. This means that technically, IP NAT is not an official Internet standard.


A basic implementation of NAT involves setting up an organization's internal network using one of the private addressing ranges set aside for local IP networks. One or more public (Internet) addresses are also assigned to the organization as well, and one or more NAT-capable routers are installed between the local network and the public Internet. The public IP addresses are like “outside lines” in the telephone system, and the private addresses are like “internal extensions”.

The NAT router plays the role of telephone system computer and receptionist. It maps internal extensions to outside lines as needed, and also handles "incoming calls" when required. It does this by not just routing IP datagrams but modifying them as needed, translating addresses in datagrams from the private network into public addresses for transmission on the Internet, and back again.

Over time, newer versions of NAT have also been created that solve other problems or provide additional capabilities. Port-Based NAT allows sharing of even more hosts on a limited number of IP addresses, by letting two or more devices share one IP address at a time. So-called “Twice NAT” helps with the implementation of virtual private networks (VPN) by translating both source and destination addresses in both incoming and outgoing datagrams.

Key Concept: IP Network Address Translation (IP NAT or NAT) is a technique that allows an organization to set up a network using private addresses, while still being able to communicate on the public Internet. A NAT-capable router translates private to public addresses and vice-versa as needed. This allows a small number of public IP addresses to be shared amongst a large number of devices, and provides other benefits as well (but also has some drawback).



Previous Topic/Section
IP Network Address Translation (NAT) Protocol
Previous Page
Pages in Current Topic/Section
12
3
45
Next Page
IP NAT Address Terminology
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $



Home - Table Of Contents - Contact Us

The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005

Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.