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!

Enjoy The TCP/IP Guide? Get the complete PDF!
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  Internet Protocol Version 4 (IP, IPv4)
                     9  IP Datagram Delivery and Routing

Previous Topic/Section
IP Routing Concepts and the Process of Next-Hop Routing
Previous Page
Pages in Current Topic/Section
12
3
Next Page
IP Routing In A Subnet Or Classless Addressing (CIDR) Environment
Next Topic/Section

IP Routes and Routing Tables
(Page 3 of 3)

Route Determination

Now, imagine that this process is expanded to handle thousands of networks and routers. Not only do routers need to know which of their local connections to use for each network, they want to know, if possible, what is the best connection to use for each network. Since routers are interconnected in a mesh there are usually multiple routes between any two devices, but we want to take the best route whenever we can. This may be the shortest route, the least congested, or the route considered optimal based on other criteria.

Determining what routes we should use for different networks turns out to be an important but very complex job. Routers must plan routes and exchange information about routes and networks, which can be done in a variety of ways. This is accomplished in IP using special IP routing protocols. It is through these protocols that R2 and R3 would find out that 14.0.0.0/8 exists and that it is connected to them via R1. I discuss these important “support protocols” in their own section.

Note: There is a difference between a routable protocol and a routing protocol. IP is a routable protocol, which means its messages (datagrams) can be routed. Examples of routing protocols are RIP or BGP, which are used to exchange routing information between routers.



Previous Topic/Section
IP Routing Concepts and the Process of Next-Hop Routing
Previous Page
Pages in Current Topic/Section
12
3
Next Page
IP Routing In A Subnet Or Classless Addressing (CIDR) Environment
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.