A quick post about one of the key pieces of information that any potential CCIE has to know in-depth; how does BGP select a path?
I have put together a large but informative flow chart that details what happens:
Click here to download a larger version of the image
I had come across this link on the internet but needed something with a bit more detail on it so I decided to ‘make my own’
The flow chart is based on information within Jeff Doyle’s ‘Routing TCP/IP, Volume 2’ and this link:
BGP Best Path Selection Algorithm
Creating the document has really helped to etch the order in my mind J
BGP won’t consider any of the above unless the next-hop is considered reachable
By: Fred Bloggs on February 27, 2008
at 6:23 pm
A valid point, I have made a presumption that the next hop is always available but I will amend the flow chart to represent your comment.
Many thanks
By: Richard @ Configureterminal.com on February 27, 2008
at 6:35 pm
Very helpful, thanks!
I’ve downloaded a copy to use for my SP exam.
By: bitbucket on February 27, 2008
at 9:52 pm
[...] found this great link from Richard Bannister’s CCIE Blog. Richard has put together a great BGP Best Path Selection flow chart that details the order in which a path is chosen. Great [...]
By: BGP Best Path Selection Algorithm | ardenpackeer.com on June 24, 2008
at 10:40 am
Hi Richard,
Just to inform you that chaeplin link is broken in the end of your article.
Nice chart, well done!
By: pello on August 22, 2008
at 9:50 am
Hi Pello,
Thanks for letting me know, luckily I had a copy saved locally on my laptop so I have uploaded it to http://rbcciequest.wordpress.com/files/2008/08/bgp_pathselection.jpg
Nice OSPF MD5-Auth hack by the way.
Thanks again
Richard
By: Richard @ Configureterminal.com on August 22, 2008
at 12:22 pm
really a awesome post.
regards
shivlu jain
By: shivlu jain on February 2, 2009
at 10:37 am
Cool. Thank you very much, very useful. Added a reference in my blog to this post
By: Nicolas on May 20, 2009
at 10:03 pm
[...] A nice chart illustrating the BGP bestpath selection process. [...]
By: 111 Articles to Help You Pass the CCIE Routing and Switching Lab Exam on October 21, 2009
at 3:00 pm
excellent illustration of the best path algorithm.
great post
By: antoniehenning on December 30, 2009
at 9:44 pm
[...] } Inspired by the flow chart that Mr Richard Bannister did for the BGP route path selection, I did one for conventional route-selection in the [...]
By: RIB Route-Selection « Routing Bits on January 7, 2010
at 4:26 pm
Very useful indeed,
By: Ruhann on January 7, 2010
at 4:44 pm
[...] The best post I have seen on the topic is this one that in detail illustrates the algorithm in a flow-chart: http://rbcciequest.wordpress.com/2008/02/27/bgp-path-selection/ [...]
By: BGP Best Path Selection Process « Bridging the gap between CCIE RS and SP on January 13, 2010
at 11:26 am
[...] This one courtesy of Richard Bannister’s CCIE Blog: [...]
By: BGP Best Path Selection « AlwaysTheNetwork on February 1, 2010
at 12:40 pm
hi richard very nice blog…
By: pradip on April 4, 2010
at 6:19 am
[...] والسلايد الثاني منقول من مدونة Richard Bannister’s CCIE Blog: [...]
By: شرح بروتوكول الـBGP (القسم الثاني) | Network Set on June 5, 2010
at 8:05 pm
[...] http://rbcciequest.wordpress.com/2008/02/27/bgp-path-selection/ [...]
By: CiscoCraze on November 23, 2010
at 5:08 am
Quite interesting…
By: bgp on June 20, 2011
at 5:25 pm
[...] found this great link from Richard Bannister’s CCIE Blog. Richard has put together a great BGP Best Path Selection flow chart that details the order in which a path is chosen. Great work! [...]
By: BGP Best Path Selection Algorithm | ardenpackeer.com on March 20, 2012
at 8:03 am
Anybody let me know to learn BGP for the scratch……
By: Janardhan on April 7, 2012
at 11:00 am
Anybody let me know a good e-book to learn BGP from scratch????
By: Janardhan on April 7, 2012
at 11:01 am
For cisco routers, start with routing TCP/IP vol2 by cisco press.
This will give you a very good start.
By: Chris G on September 11, 2012
at 9:03 am