Prerequisites: CCNP level skills.
Note!
Configuration from Lab 123 must be used in this lab.
Topology
Task 1
After merging the three ASes (Lab 123), prefixes advertised by AS 40 and AS 50 prepend local-as AS numbers. Configure routers in such a way that the local-AS numbers no longer get propagated within AS 123 and to other autonomous systems.
Solution
Task 1
After merging the three ASes (Lab 123), prefixes advertised by AS 40 and AS 50 prepend local-as AS numbers. Configure routers in such a way that the local-AS numbers no longer get propagated within AS 123 and to other autonomous systems.
Pic. 2 - R3's Local-AS on R1.
Pic. 3 - R3's Local-AS on R3.
R3 is DIRECTLY connected to AS 50 (R5) and also shows AS 30 (local-as) in the AS_PATH
Pic. 4 - R3's Local-AS on R4.
Only one prefix is shown as an example. On R3 you can use:
show ip bgp regexp _40$.
AS 10 and AS 20 also show in the AS_PATH attribute.
R1 Configuration:
!
router bgp 123
no synchronization
bgp router-id 172.16.101.1
bgp log-neighbor-changes
network 172.16.101.0 mask 255.255.255.0
neighbor 10.1.13.3 remote-as 123
neighbor 10.1.13.3 next-hop-self
neighbor 10.1.14.4 remote-as 40
neighbor 10.1.14.4 local-as 10 no-prepend
no auto-summary
no synchronization
bgp router-id 172.16.101.1
bgp log-neighbor-changes
network 172.16.101.0 mask 255.255.255.0
neighbor 10.1.13.3 remote-as 123
neighbor 10.1.13.3 next-hop-self
neighbor 10.1.14.4 remote-as 40
neighbor 10.1.14.4 local-as 10 no-prepend
no auto-summary
!
R2 Configuration:
!
router bgp 123
no synchronization
bgp router-id 172.16.102.2
bgp log-neighbor-changes
network 172.16.102.0 mask 255.255.255.0
neighbor 10.1.23.3 remote-as 123
neighbor 10.1.23.3 next-hop-self
neighbor 10.1.24.4 remote-as 40
neighbor 10.1.24.4 local-as 20 no-prepend
no auto-summary
no synchronization
bgp router-id 172.16.102.2
bgp log-neighbor-changes
network 172.16.102.0 mask 255.255.255.0
neighbor 10.1.23.3 remote-as 123
neighbor 10.1.23.3 next-hop-self
neighbor 10.1.24.4 remote-as 40
neighbor 10.1.24.4 local-as 20 no-prepend
no auto-summary
!
R3 Configuration:
!
router bgp 123
no synchronization
bgp router-id 172.16.103.3
bgp log-neighbor-changes
network 172.16.103.0 mask 255.255.255.0
neighbor 10.1.13.1 remote-as 123
neighbor 10.1.13.1 route-reflector-client
neighbor 10.1.13.1 next-hop-self
neighbor 10.1.23.2 remote-as 123
neighbor 10.1.23.2 route-reflector-client
neighbor 10.1.23.2 next-hop-self
neighbor 10.1.35.5 remote-as 50
neighbor 10.1.35.5 local-as 30 no-prepend
no auto-summary
no synchronization
bgp router-id 172.16.103.3
bgp log-neighbor-changes
network 172.16.103.0 mask 255.255.255.0
neighbor 10.1.13.1 remote-as 123
neighbor 10.1.13.1 route-reflector-client
neighbor 10.1.13.1 next-hop-self
neighbor 10.1.23.2 remote-as 123
neighbor 10.1.23.2 route-reflector-client
neighbor 10.1.23.2 next-hop-self
neighbor 10.1.35.5 remote-as 50
neighbor 10.1.35.5 local-as 30 no-prepend
no auto-summary
!
Verification:
Pic. 5 - R1 Has No AS 30 in AS_PATH.
Pic. 6 - R4 Has No AS 30 in AS_PATH.
