FortiGate
FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
msanjaypadma
Staff
Staff
Article Id 205708
Description

This article describes how to skip the best AS-PATH criteria while selecting the best route in the BGP routing protocol.

Scope

To ignore/skip shortest AS_PATH selection process from BGP best path selection algorithm.

Solution

In the BGP routing protocol, selecting a specific (destination) prefix/route as best will go through the BGP attribute and path selection process.

When it comes to AS-PATH selection i.e. the prefix which is having the shortest (least) AS-PATH it will select as the best route.

 

To ignore/skip this AS-path selection process from the BGP best-path selection algorithm, use "set bestpath-as-path-ignore enable" in BGP router configuration mode.

 

Command:

 

#config router bgp

#set bestpath-as-path-ignore enable

#end

 

Example:

 

msanjaypadma_5-1645995359294.png

 

 

  • Spoke firewall receiving prefix 1.1.1.1/32 from both ISP1 [AS-65001] and ISP2 [AS-65002]
  • Currently, the best route has been selected via ISP2 due to the shortest AS Path. 
    msanjaypadma_2-1645992915010.png
  • After applying bestpath-as-path-ignore, reset the bgp connection for ISP2[AS-65002]
    msanjaypadma_3-1645994049336.png
  • Now the best path has been selected of ISP1[AS-65001]
    msanjaypadma_4-1645994535732.png

     

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