Thx for sharing your comments. As a consequence, i have made some changes and update the tutorial. Tutorial can be browsed on the site or downloaded as PDF in the download section of the site(version 0.94).

Executive Summary on this article.

The aim is to give a demonstration on how to use BGP and understand it in a world of interconnected ISPs. The contents describe practices and techniques about an ISP customer who:
– buys IP transit connectivity from different ISPs.
– needs to implement a load-balancing process.
– inserts redundancy and multihoming options for the Internet provision in case of link failure.

– The first chapter introduces the design of the network and its topology for the study case. You will find diagrams on the BGP and Static design; the traffic engineering targeted configuration, and a listing of IP-addresses and interfaces used.

Notions described:

Chapter A : The second chapter (chapter A) highlights various global notions on BGP, which are a necessity to understand. This is in order to be able to design and configure the network described in this study case, which aims to deliver IP transit services to customer, and uses multihoming connectivity to several ISPs. The general points of BGP in this chapter are related to a way of thinking within an ISP environment. People can overview it, but it is recommended to read it accurately if they do not practice BGP administration every day.

– Traffic engineering BGP tools
– peering agreement between ISPs
– relations between packets, routes announcement, ingress, inbound, egress, outbound traffic
– BGP local preference attribute,
– BGP prepend
– BGP communities, community guide, setup, and understanding
– BGP Next-hop, next-hop-self,
– BGP Recursive lookup
– BGP loop prevention, as-apth loop prevention, split-horizon mechanism
 – BGP common setup commands
– BGP basic multihoming template

Chapter B: The 3rd chapter (chapter B) targets the design directly and its configuration. Ebgp and Ibgp configurations are described and deeply explained. Peering agreements and multihoming are enlightened in a practical way.

– BGP tools and practices for return traffic: as-path prepend, LocalPreference or BGP communities
– Ebgp analysis, method discussions and setup regarding the study case
– Ibgp analysis, method discussions and setup regarding the study case
– network pools aggregation
– Ibgp and Ebgp template

Chapter C: The last chapter (chapter C) validates the configuration of ChapterB, and more generally the study case. Scenarios of links failures are presented, in order to check up if the multihoming configuration agrees the design and the traffic engineering objectives. Moreover, verifications, monitoring and debug commands are also stressed, in order to validate the setup.

– BGP monitoring tools and analysis discussion methods
– Ebgp traffic method tests and discussions
– Multihoming, redundancy traffic tests and analysis
– BGP common debug and monitoring commands for ingress and egress traffic