CCNP实验:BGP路由黑洞之路由反射器(Router Reflector)解决
【实验环境】
C3640-IK9O3S-M Version 12.4(10)
【实验目的】
采用路由反射器(Router Reflector)解决由IBGP水平分割导致的BGP路由黑洞问题
【实验拓扑】
【实验描述】
R1、R2、R4、R5跑BGP协议，R2、R3、R4跑OSPF协议。目标是使1.1.1.1<->5.5.5.5可以互相访问
IBGP邻居关系采用回环口进行建立
R1<->R2、R4<->R5之间使用直连接口建立EBGP关系
数据层面的BGP路由黑洞问题：由于R3没有跑BGP，因此R2和R4均不会将路由条目传给R3，因此R3没有1.1.1.1和5.5.5.5的路由，导致路由黑洞。如果在R3上跑BGP，与R2和R4建立IBGP关系，又会因为IBGP水平分割导致R2、R4路由学习不完整。
解决方法：利用路由反射器，将R3作为反射器(RR)，其余IBGP路由器作为客户端(C)，路由反射器和其客户端共同组成路由反射簇，客户端只需要与路由反射器建立邻居即可，不需要与每台IBGP路由器建立邻居。
路由反射器的规则：
1、RR从EBGP收到的路由，会反射给客户端和非客户端；
2、从客户端收到的路由，会反射给客户端、非客户端及EBGP邻居；
3、从非客户端收到的路由，只会反射给客户端和EBGP邻居，不会反射给其他非客户端。
【实验步骤】
1、R1基本配置，端口:
!
interface Loopback0
ip address 1.1.1.1 255.255.255.0
!
interface Serial0/0
ip address 12.0.0.1 255.255.255.0
clock rate 64000
!
2、R2基本配置，端口，OSPF:
!
interface Loopback0
ip address 2.2.2.2 255.255.255.0
!
interface Serial0/0
ip address 12.0.0.2 255.255.255.0
!
interface Serial0/1
ip address 23.0.0.1 255.255.255.0
clock rate 64000
!
router ospf 110
router-id 2.2.2.2
network 2.2.2.0 0.0.0.255 area 0
network 23.0.0.1 0.0.0.0 area 0
!
3、R3基本配置，端口，OSPF:
!
interface Loopback0
ip address 3.3.3.3 255.255.255.0
!
interface Serial0/0
ip address 34.0.0.1 255.255.255.0
clock rate 64000
!
interface Serial0/1
ip address 23.0.0.2 255.255.255.0
!
router ospf 110
router-id 3.3.3.3
network 3.3.3.0 0.0.0.255 area 0
network 23.0.0.2 0.0.0.0 area 0
network 34.0.0.1 0.0.0.0 area 0
!
4、R4基本配置，端口，OSPF:
!
interface Loopback0
ip address 4.4.4.4 255.255.255.0
!
interface Serial0/0
ip address 34.0.0.2 255.255.255.0
!
interface Serial0/1
ip address 45.0.0.1 255.255.255.0
clock rate 64000
!
router ospf 110
router-id 4.4.4.4
network 4.4.4.0 0.0.0.255 area 0
network 34.0.0.2 0.0.0.0 area 0
!
5、R5基本配置，端口:
!
interface Loopback0
ip address 5.5.5.5 255.255.255.0
!
interface Serial0/1
ip address 45.0.0.2 255.255.255.0
!
6、配置R1与R2之间的EBGP
//R1配置AS 1
router bgp 1
no synchronization
bgp router-id 1.1.1.1
network 1.1.1.0 mask 255.255.255.0
neighbor 12.0.0.2 remote-as 3
no auto-summary
//R2配置AS 3
router bgp 3
no synchronization
bgp router-id 2.2.2.2
neighbor 12.0.0.1 remote-as 1
no auto-summary
7、配置R4与R5之间的EBGP
//R4配置AS 3
router bgp 3
no synchronization
bgp router-id 4.4.4.4
neighbor 45.0.0.2 remote-as 5
no auto-summary
//R5配置AS 5
router bgp 5
no synchronization
bgp router-id 5.5.5.5
network 5.5.5.0 mask 255.255.255.0
neighbor 45.0.0.1 remote-as 3
no auto-summary
8、使用回环接口配置R2、R3、R4之间的IBGP关系
//R3配置
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 4.4.4.4 remote-as 3
neighbor 4.4.4.4 update-source Loopback0
no auto-summary
//R2配置
router bgp 3
neighbor 3.3.3.3 remote-as 3
neighbor 3.3.3.3 update-source Loopback0
nei 3.3.3.3 next-hop-self
//R4配置
router bgp 3
neighbor 3.3.3.3 remote-as 3
neighbor 3.3.3.3 update-source Loopback0
nei 3.3.3.3 next-hop-self
9、在R3上开启路由反射器，指定客户端
router bgp 3
neighbor 2.2.2.2 route-reflector-client
neighbor 4.4.4.4 route-reflector-client
10、查看R3的路由表
R3#sh ip bgp
BGP table version is 3, local router ID is 3.3.3.3
Network Next Hop Metric LocPrf Weight Path
*>i1.1.1.0/24 2.2.2.2 0 100 0 1 i
*>i5.5.5.0/24 4.4.4.4 0 100 0 5 i
11、验证R1与R5回环口连通性
R1#ping 5.5.5.5 so 1.1.1.1
Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 188/325/496 ms
12、在R2上查看反射路由条目5.5.5.0/24
R2#sh ip bgp 5.5.5.0/24
BGP routing table entry for 5.5.5.0/24, version 3
Paths: (1 available, best #1, table Default-IP-Routing-Table)
4.4.4.4 (metric 129) from 3.3.3.3 (3.3.3.3)
Origin IGP, metric 0, localpref 100, valid, internal, best
Originator: 4.4.4.4, Cluster list: 3.3.3.3
13、在R4上查看反射路由条目1.1.1.0/24
R4#sh ip bgp 1.1.1.0/24
BGP routing table entry for 1.1.1.0/24, version 3
Paths: (1 available, best #1, table Default-IP-Routing-Table)
2.2.2.2 (metric 129) from 3.3.3.3 (3.3.3.3)
Origin IGP, metric 0, localpref 100, valid, internal, best
Originator: 2.2.2.2, Cluster list: 3.3.3.3
14、评价
路由反射器相对于邻居全互联来说，简化了配置和数量，因为IBGP邻居关系只需要在客户端与RR之间建立即可。