Local Preference

Now again check in R5 and see the bgp routing table.

R5#sh ip bgp

BGP table version is 12, local router ID is 150.5.5.5

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

              r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path

*> 4.1.0.0/24       155.1.35.3                            10 100 400 i

*                             150.4.4.4                0             0 400 i

*> 4.2.0.0/24       155.1.35.3                            10 100 400 i

*                             150.4.4.4                0             0 400 i

*> 4.3.0.0/24       155.1.35.3                            10 100 400 i

*                              150.4.4.4                0             0 400 i

Note by default the local preference will be set to default because the local preference are not exchanged between eBGP peers.

Now R5 selecting the prefix 4.x.0.0/24 as best path via R3(155.1.35.3) because the weight via R3 is high so lets make the weight equals.

R5(config)#router bgp 500

R5(config-router)#neighbor 150.4.4.4 weight 10

R5#sh ip bgp

BGP table version is 15, local router ID is 150.5.5.5

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

              r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path

*  4.1.0.0/24       155.1.35.3                            10 100 400 i

*>                         150.4.4.4                0            10 400 i

*  4.2.0.0/24       155.1.35.3                            10 100 400 i

*>                         150.4.4.4                0            10 400 i

*  4.3.0.0/24       155.1.35.3                            10 100 400 i

*>                          150.4.4.4                0            10 400 i

Now again the tie breaker here is shortest AS path that is via R4. Change the local preference and verify the output.

R5(config)#route-map R3

R5(config-route-map)#set local-preference 200

R5(config)#router bgp 500

R5(config-router)#neighbor 155.1.35.3 route-map R3 in

R5#sh ip bgp

BGP table version is 23, local router ID is 150.5.5.5

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

              r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path

*> 4.1.0.0/24       155.1.35.3                    200     10 100 400 i

*                             150.4.4.4                0            10 400 i

*> 4.2.0.0/24       155.1.35.3                    200     10 100 400 i

*                             150.4.4.4                0            10 400 i

*> 4.3.0.0/24       155.1.35.3                    200     10 100 400 i

*                             150.4.4.4                0            10 400 i

Here the best path via R3 since the local preference is high than R4.