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BGP As-path prepending – Use cases, Alternatives and Challenges

BGP As-path is a mandatory BGP attribute which has to be sent in every BGP message. BGP as-path prepending is one of the BGP traffic engineering methods which will be explained in detail throughout this post. 



What is BGP As-path attribute ? Why BGP as-path attribute is used ?

What is BGP as-path prepending ?

What are the other alternatives for BGP as-path prepending ?

How BGP traffic engineering is achieved with BGP as-path prepending ?

What are the challenges which BGP as-path prepending cannot handle and what are the solutions for incoming BGP path selections.

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Orhan Ergun 1 Comment

What is DFZ (Default Free Zone)?

In the context of the Internet and BGP routing, DFZ – commonly known as Default Free Zone – refers to the collections of all the public IPv4 BGP prefixes without default route on the global Internet.

Most of the time, you hear full-route or full-Internet-route terms which are the same with Default Free Zone term. Having all BGP routes, which are announced by all the available AS (Autonomous System), on the Internet.

Currently, there are more than 600,000 IPv4 BGP routes and about 30,000 IPv6 routes in the DFZ (Default Free Zone).  These numbers, however, could easily be reduced to 300,000 for IPv4 and less than 20,000 for IPv6 based on the CIDR reports (IPv4 CIDR report and  IPv6 CIDR report). Read more