Lab 123 - BGP Local-AS

Prerequisites: CCNP level skills.

Topology

Pic. 1 - Topology Diagram.

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

Task 1
Three autonomous systems: AS 10 (R1), AS 20 (R2), and AS 30 (R3) merge into one AS 123. They will be running OSPF 1 Area 0 on internal links. Configure OSPF and BGP on these routers in AS 123 and advertise their loopbacks into BGP.

Task 2
R4 is still configured to peer with AS 10 (R1) and AS 20 (R2). R5 is still configured to peer with AS 30 (R3). Make sure the peering works between them withouth changing configuration on R4 and R5. All routers in AS 123 should be able to reach prefixes advertised by AS 40 and AS 50.

Solution

Task 1
Three autonomous systems: AS 10 (R1), AS 20 (R2), and AS 30 (R3) merge into one AS 123. They will be running OSPF 1 Area 0 on internal links. Configure OSPF and BGP on these routers in AS 123 and advertise their loopbacks into BGP.

R1 Configuration:

!

router ospf 1
 router-id 172.16.101.1
 log-adjacency-changes
 network 10.1.13.1 0.0.0.0 area 0
!
!
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
 no auto-summary
!

R2 Configuration:

!

router ospf 1
 router-id 172.16.102.2
 log-adjacency-changes
 network 10.1.23.2 0.0.0.0 area 0
!
!
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
 no auto-summary
! 

R3 Configuration:

!

outer ospf 1
 router-id 172.16.103.3
 log-adjacency-changes
 network 10.1.13.3 0.0.0.0 area 0
 network 10.1.23.3 0.0.0.0 area 0
!
!
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
 no auto-summary

!

Verification:

Pic. 2 - R3's BGP Peers.

Pic. 3 - Connectivity Test on R1.

Task 2

R4 is still configured to peer with AS 10 (R1) and AS 20 (R2). R5 is still configured to peer with AS 30 (R3). Make sure the peering works between them withouth changing configuration on R4 and R5. All routers in AS 123 should be able to reach prefixes advertised by AS 40 and AS 50.

R4 Configuration:

!

router bgp 40
 no synchronization
 bgp router-id 172.16.104.4
 bgp log-neighbor-changes
 network 172.16.104.0 mask 255.255.255.0
 network 172.16.144.0 mask 255.255.255.0
 redistribute connected route-map CONN_TO_BGP
 neighbor 10.1.14.1 remote-as 10
 neighbor 10.1.24.2 remote-as 20
 no auto-summary

!

R5 Configuration:

!

router bgp 50
 no synchronization
 bgp router-id 172.16.105.5
 bgp log-neighbor-changes
 network 172.16.105.0 mask 255.255.255.0
 neighbor 10.1.35.3 remote-as 30
 no auto-summary

!

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 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 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 auto-summary

!

Verification:

Pic. 4 - R4's BGP Peering.

Pic. 5 - R5's BGP Peering.

Ping check: verified the reachability (no picture to make this post shorter).