Lab 101 - BGP Path Selection Using Origin

Prerequisites: CCNP level skills.

Topology

Personal Note!

This week I'm in Mechelen, Belgium. My poor laptop barely handles four dynamips instances :(.

Pic. 1 - Topology Diagram.

Icons designed by: Andrzej Szoblik - http://www.newo.pl

Task 1
Configure BGP according to the topology diagram (pic. 1). On R1 and R2 advertise 10.1.12.0/24.

Task 2
On R3 use the origin code to prefer R2 towards 10.1.12.0/24.

Lab Solution

Task 1

Configure BGP according to the topology diagram (pic. 1). On R1 and R2 advertise 10.1.12.0/24.

R1 Configuration:

!

router bgp 20
 no synchronization
 bgp router-id 172.16.101.1
 bgp log-neighbor-changes
 network 10.1.12.0 mask 255.255.255.0
 neighbor 10.1.12.2 remote-as 20
 neighbor 10.1.13.3 remote-as 30
 no auto-summary

!

R2 Configuration:

!

router bgp 20
 no synchronization
 bgp router-id 172.16.102.2
 bgp log-neighbor-changes
 network 10.1.12.0 mask 255.255.255.0
 neighbor 10.1.12.1 remote-as 20
 neighbor 10.1.23.3 remote-as 30
 no auto-summary

!

R3 Configuration:

!

router bgp 30
 no synchronization
 bgp router-id 172.16.103.3
 bgp log-neighbor-changes
 neighbor 10.1.13.1 remote-as 20
 neighbor 10.1.23.2 remote-as 20
 no auto-summary

!

Task 2
On R3 use the origin code to prefer R2 towards 10.1.12.0/24.

Pic. 2 - BGP Table on R3.

Notice!

R1 is the gateway towards 10.1.12.0/24 now.

R3 Configuration:

!

ip prefix-list AS20_PREFIX seq 5 permit 10.1.12.0/24
!

route-map SET_ORIGIN permit 10
 match ip address prefix-list AS20_PREFIX
 set origin incomplete
route-map SET_ORIGIN permit 999
!

router bgp 30
 no synchronization
 bgp router-id 172.16.103.3
 bgp log-neighbor-changes
 neighbor 10.1.13.1 remote-as 20
 neighbor 10.1.13.1 route-map SET_ORIGIN in
 neighbor 10.1.23.2 remote-as 20
 no auto-summary

!

Verification:

Pic. 3 - BGP Table on R3.