BGP Lab 13 BGP AS-path prepending (CCNP Level)

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Download Lab: GNS3

Image requirements:
 Cisco IOSv        (vios-adventerprisek9-m.vmdk.SPA.156-2.T)


Introduction:

AS-path is the strongest attribute since it is the main mechanism for loop prevention in BGP networks, also it is a great tool to influence route selection, it works both ways inbound and outbound depending on how you will apply the route-map to the bgp neighbor command in or out, in this lab, you will configure both ways.


Lab tasks:

1. Configure router ISP4 to prepend every prefix coming from AS101 three times. (Inbound)

2. Configure router ISP2 to prepend only its own AS's prefix two times when it sends prefixes to AS103. (Outbound)


Configuration example:
!
R1(config)# route-map AS-PREPEND permit 10
R1(config-route-map)# set as-path prepend 101 101 101
R1(config-route-map)# exit
!
R1(config)# router bgp 104
R1(config-router)# neighbor 50.0.0.100 route-map AS-PREPEND in


Topology: