BGP为了解决环路问题，设计了IBGP水平分割原则：从IBGP邻居收到的路由不再传递给其他IBGP邻居。但这产生了路由黑洞、路由学习不完整一系列问题。上一篇《解决BGP路由黑洞：联邦》通过联邦打破了IBGP水平分割，但解决问题并非只有一种方法，这里使用另一种方法：路由反射器。

路由反射器（Router Reflector）是典型的C/S模型，RR作为服务器（Server），它的IBGP邻居可以设置为客户端（Client）和非客户端（Non-Client），规则如下：

1.RR通过EBGP邻居学习到的路由，会传递给其他EBGP邻居（如果有）、Client以及Non-Client

2.RR通过Client（IBGP邻居）学习到的路由，会传递给EBGP邻居（如果有）、其他Client以及Non-Client

3.RR通过Non-Client（IBGP邻居）学习到的路由，只会传递给EBGP邻居（如果有）和Client 其实总结起来很简单：RR在传递路由时候，Client跟EBGP邻居具有相同的待遇。

配置命令：

bgp neighbor x.x.x.x router-reflector-client          //将本路由设置为RR，同时将x.x.x.x设置为Client

在这个拓扑中，只要将R3设置为RR，R2、R3任意一个设置为Client就能打破IBGP水平分割，但建议把R2,R3都设置成Client。

R1配置

interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!
interface Serial0/0
 ip address 192.168.12.1 255.255.255.0

! 
router bgp 1
 no synchronization
 bgp router-id 1.1.1.1
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.0
 neighbor 192.168.12.2 remote-as 3
 no auto-summary
!

R2配置

interface Loopback0
 ip address 2.2.2.2 255.255.255.0
!
interface Serial0/0
 ip address 192.168.12.2 255.255.255.0

!         
interface Serial0/1
 ip address 192.168.23.2 255.255.255.0
!
router ospf 110
 router-id 2.2.2.2
 network 2.2.2.2 0.0.0.0 area 0
 network 192.168.23.2 0.0.0.0 area 0
router bgp 3
 no synchronization
 bgp router-id 2.2.2.2
 neighbor 3.3.3.3 remote-as 3
 neighbor 3.3.3.3 update-source Loopback0
 neighbor 3.3.3.3 next-hop-self
 neighbor 192.168.12.1 remote-as 1
 no auto-summary
!

R3配置

interface Loopback0
 ip address 3.3.3.3 255.255.255.0
!
interface Serial0/0
 ip address 192.168.34.3 255.255.255.0
!         
interface Serial0/1
 ip address 192.168.23.3 255.255.255.0
!
router ospf 110
 router-id 3.3.3.3
  network 3.3.3.3 0.0.0.0 area 0
 network 192.168.23.3 0.0.0.0 area 0
 network 192.168.34.3 0.0.0.0 area 0
router bgp 3
 no synchronization
 bgp router-id 3.3.3.3
 neighbor 2.2.2.2 remote-as 3
 neighbor 2.2.2.2 update-source Loopback0
 neighbor 2.2.2.2 route-reflector-client
 neighbor 4.4.4.4 remote-as 3
 neighbor 4.4.4.4 update-source Loopback0
 neighbor 4.4.4.4 route-reflector-client
 no auto-summary
!

R4配置

interface Loopback0
 ip address 4.4.4.4 255.255.255.0
!
interface Serial0/0
 ip address 192.168.34.4 255.255.255.0
 serial restart-delay 0
!         
interface Serial0/1
 ip address 192.168.45.4 255.255.255.0
!
router ospf 110
 router-id 4.4.4.4
  network 4.4.4.4 0.0.0.0 area 0
 network 192.168.34.4 0.0.0.0 area 0
router bgp 3
 no synchronization
 bgp router-id 4.4.4.4
 neighbor 3.3.3.3 remote-as 3
 neighbor 3.3.3.3 update-source Loopback0
 neighbor 3.3.3.3 next-hop-self
 neighbor 192.168.45.5 remote-as 5
 no auto-summary
!

R5配置

interface Loopback0
 ip address 5.5.5.5 255.255.255.0
!            
interface Serial0/1
 ip address 192.168.45.5 255.255.255.0
!
router bgp 5
 no synchronization
 bgp router-id 5.5.5.5
 bgp log-neighbor-changes
 network 5.5.5.0 mask 255.255.255.0
 neighbor 192.168.45.4 remote-as 3
 no auto-summary
!