BGP Weight Configuration Example [GNS3 Lab]

What is BGP Weight

  • Weight: Weight is a Cisco-defined BGP attribute that is local to a router. The weight attribute is not advertised to neighboring routers.  If the router learns about more than one route to the same destination, the route with the highest weight will be preferred.


Topology


Before manipulating the path via Weight, let’s check which neighbor was originally selected to get to the route 4.4.4.4/32:

R1#sh ip bgp
BGP table version is 2, local router ID is 172.16.30.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *  4.4.4.4/32         172.16.20.2                            0 65552 65554 i
 *>                    172.16.30.2                            0 65553 65554 i


So, the neighbor R3 was selected for route 4.4.4.4/32, let’s dive into the configuration of the BGP weight of router R1.

BGP Weight configuration

router bgp 65551
 bgp log-neighbor-changes
 neighbor 172.16.20.2 remote-as 65552
 neighbor 172.16.20.2 route-map Weight-400 in
 neighbor 172.16.30.2 remote-as 65553
 neighbor 172.16.30.2 route-map Weight-300 in


route-map Weight-400 permit 10
 set weight 400
!
route-map Weight-300 permit 10
 set weight 300


Verifications

R1#show ip bgp
BGP table version is 2, local router ID is 172.16.30.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  4.4.4.4/32       172.16.20.2                          400 65552 65554 i
 *                    172.16.30.2                          300 65553 65554 i
R1#




https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClszCAC

Bilel A

Bilel A

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