For visitors or readers looking for information on BGP loop prevention, and does not want to read all the complete tutorial, i will point them to these parts of the tutorial.

For BGP loop prevention within an AS, or Ibgp loop prevention based on Split-horizon mechanisms, plz read the following pages :

• p29 to p31 of the tutorial(pdf) in download section
• or go here : A.5.b) Ibgp loop prevention: “split-horizon” mechanism

For BGP loop prevention between different ASs, or ISPs, which is a very important notion to understand when u are confronted to build a network with multihoming, redundancy and link failure options, plz read the following pages. As-path attribute allow ebgp loop prevention.

However the concept of BGP loop between ISPs or different ASs is very tricky since this is not something that you can experience in your own network. You will be more likely victim of it, particularly if your traffic engineering redundancy case has not been fully tested. I will even say that ebgp loop prevention is mainly related to peering agreements betweens ISPs.

This is deeply explained though the tutorial, but the four following sections are sufficient to make a clear outlook.

1)Presentation of the network implemented through the study-case

• p8 to p11 of the tutorial(pdf) in download section
• or go here :  I.2) Overview of the study case: BGP tutorial , best practices and multihoming techniques on ISP proposing IP transit services.
  and here : I.3) Bandwidth Planning and Provisioning for load-balancing features.

2) Peering agreement between the upstream/transit providers

• p16 to p17 of the tutorial(pdf) in download section
• or go here : A.2.b) Peering agreement between the upstream/transit providers

3) Ebgp loop prevention mechanism based on as-path attribute

• p27 to p28 of the tutorial(pdf) in download section
• or go here : A.5.a) Ebgp loop prevention mechanism based on as-path attribute

4) Observations and commentaries of the results and the redundancy scenarios.

• p74 to 84 of the tutorial(pdf) in download section
• or go here : C.1) Observations and commentaries of the results and the redundancy scenarios.