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.
|
|
|
|
IP Classless Addressing: Classless Inter-Domain Routing (CIDR) / "Supernetting"
As the early Internet began to grow
dramatically, three
main problems arose with the original classful addressing
scheme. These difficulties were addressed
partially through subnet
addressing, which provides more flexibility
for the administrators of individual networks on an internet. Subnetting,
however, doesn't really tackle the problems in general terms. Some of
these issues remain due to the use of classes even with subnets.
While development began on IP
version 6 and its roomy
128-bit addressing system in the mid-1990s,
it was recognized that it would take many years before widespread deployment
of IPv6 would be possible. In order to extend the life of IP version
4 until the newer IP version 6 could be completed, it was necessary
to take a new approach to addressing IPv4 devices. This new system calls
for eliminating the notion of address classes entirely, creating a new
classless addressing scheme sometimes called Classless Inter-Domain
Routing (CIDR).
In this section I describe modern
classless IP addressing. I begin with an overview of the concepts behind
classless addressing and the idea behind supernetting, including
why it was created and what its advantages and disadvantages are. I
then define CIDR and describe how the system works in more detail, including
the notation used for address blocks. I list each of the CIDR address
block sizes and show how they relate to the older class A, B and C networks.
I conclude with an example of CIDR addressing, which is similar to the
practical subnetting section prior to this one, but focused on CIDR
and a bit more condensed.
Background Information: Classless IP addressing represents the latest evolution of IP addressing, following on the heels of subnetting and the original classful addressing system described in preceding sections. Understanding classless IP addressing and routing requires at least some familiarity with these older IP addressing methods. If you have come to this section without reading the preceding sections on classful addressing and subnetting, I strongly advise reviewing them first. If you understand subnetting but aren't familiar with how Variable Length Subnet Masking (VLSM) works, reading the topic on VLSM is a good idea, since CIDR is similar to VLSM in many ways. |
Quick navigation to subsections and regular topics in this 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! |
|
|
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.
|