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!

Get The TCP/IP Guide for your own computer.
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  TCP/IP Routing Protocols (Gateway Protocols)

Previous Topic/Section
Enhanced Interior Gateway Routing Protocol (EIGRP)
Previous Page
Pages in Current Topic/Section
1
Next Page
TCP/IP Border Gateway Protocol (BGP/BGP-4)
Next Topic/Section

TCP/IP Exterior Gateway/Routing Protocols (BGP and EGP)

For ease of administration, routers on large internetworks are grouped into autonomous systems (ASes) that are independently controlled by different organizations and companies. Interior routing protocols such as RIP and OSPF are used to communicate routing information between routers within an autonomous system. Obviously, if interior routing protocols are used within ASes, we need another set of routing protocols to send that information between ASes. These are called exterior routing protocols.

The entire point of autonomous system architecture is conveyed in the meaning of the first word in that phrase: autonomous. The details of what happens within an AS are hidden from other ASes, which allows the administrator of an AS to have the independence to control how he or she runs it, including the selection of one or more from a variety of different interior routing protocols. In contrast, to reliably connect ASes together, it is essential that each one be running the same exterior routing protocol, or the result would be something akin to the Tower of Babel. The result of this is that in TCP/IP there is generally only one exterior routing protocol in widespread use at a given time.

In this section I describe two different TCP/IP exterior routing protocols. The first is the Border Gateway Protocol (BGP), the one used in modern TCP/IP. BGP is very important since it is used on the current Internet and other larger internetworks, so it is covered in considerable detail. The second is the Exterior Gateway Protocol (EGP). This is an obsolete protocol that was used for communication between non-core routers and the router core in the early Internet, and is described briefly for both completeness and historical interest.

Background Information: I am assuming in this section that you are already at least somewhat familiar with interior routing protocols, at least to the extent of understanding what they do in basic terms. If you have not yet read up on RIP, the most common interior routing protocol, you may wish to skim that section. At the very least, make sure you are familiar with the overview of routing protocol architectures.


Quick navigation to subsections and regular topics in this section



Previous Topic/Section
Enhanced Interior Gateway Routing Protocol (EIGRP)
Previous Page
Pages in Current Topic/Section
1
Next Page
TCP/IP Border Gateway Protocol (BGP/BGP-4)
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.