LAB: BGP BestPath Selection - Origin

- Using Origin attribute configure AS 200 so that traffic from AS 100 going to AS 254 enters via the link between R4 and R5.

configuration

R3

router bgp 200
 no synchronization
 bgp log-neighbor-changes
 neighbor 155.1.0.5 remote-as 200
 neighbor 155.1.13.1 remote-as 100
 neighbor 155.1.13.1 route-map TO_R1 out
 neighbor 155.1.23.2 remote-as 200
 neighbor 155.1.23.2 route-reflector-client
 neighbor 155.1.37.7 remote-as 300
 neighbor 155.1.58.8 remote-as 200
 neighbor 155.1.58.8 route-reflector-client
 neighbor 155.1.108.10 remote-as 200
 neighbor 155.1.108.10 route-reflector-client
 no auto-summary
!
!
ip as-path access-list 1 permit _254$
!
!
route-map TO_R1 permit 10
 match as-path 1
 set origin incomplete
!
route-map TO_R1 permit 100

R4

router bgp 200
 no synchronization
 bgp log-neighbor-changes
 neighbor 155.1.0.2 remote-as 200
 neighbor 155.1.0.2 route-reflector-client
 neighbor 155.1.23.3 remote-as 200
 neighbor 155.1.45.4 remote-as 100
 neighbor 155.1.45.4 route-map TO_R4 out
 neighbor 155.1.58.8 remote-as 200
 neighbor 155.1.58.8 route-reflector-client
 neighbor 155.1.108.10 remote-as 200
 neighbor 155.1.108.10 route-reflector-client
 no auto-summary
!
ip as-path access-list 1 permit _254$
!
!
route-map TO_R4 permit 10
 match as-path 1
 set origin igp
!
route-map TO_R4 permit 100

verification:

Rack1R1#show ip bgp regexp _254$
BGP table version is 35, local router ID is 150.1.1.1
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
*>i205.90.31.0      155.1.45.5               0    100      0 200 254 i
*                   155.1.13.3                             0 200 254 ?
*>i220.20.3.0       155.1.45.5               0    100      0 200 254 i
*                   155.1.13.3                             0 200 254 ?
*>i222.22.2.0       155.1.45.5               0    100      0 200 254 i
*                   155.1.13.3                             0 200 254 ?

Rack1R4#show ip bgp regexp _254$
BGP table version is 31, local router ID is 150.1.4.4
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
*> 205.90.31.0      155.1.45.5                             0 200 254 i
*> 220.20.3.0       155.1.45.5                             0 200 254 i
*> 222.22.2.0       155.1.45.5                             0 200 254 i

R6 is a bit different because route to Sw1 has a longer path so it chooses R5, so the origin doesnt count in the decision process.


Rack1R6# show ip bgp regexp _254$
BGP table version is 18, local router ID is 150.1.6.6
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
*  205.90.31.0      155.1.67.7                             0 300 200 254 ?
*>i                 155.1.45.5               0    100      0 200 254 i
*  220.20.3.0       155.1.67.7                             0 300 200 254 ?
*>i                 155.1.45.5               0    100      0 200 254 i
*  222.22.2.0       155.1.67.7                             0 300 200 254 ?
*>i                 155.1.45.5               0    100      0 200 254 i