17、BGP配置之Local_Preference 选路

一、实验拓扑

二、实验需求

1、如图所示配置全网互通。

2、所有设备均能学习到环回地址。

3、AS100和AS300发布10.0.45.0和10.0.54.0到BGP中。

4、R1访问10.0.45.0从R3走，通过修改Local_Preference（本地优先级）实现。

三、实验过程

1、R1的配置

sys
un in en
sys R1
int g0/0/0
ip add 10.0.12.1 24
int g0/0/1
ip add 10.0.13.1 24
int loo0
ip add 1.1.1.1 32

ospf 1 router-id 1.1.1.1
area 0
net 10.0.12.0 0.0.0.255
net 10.0.13.0 0.0.0.255
net 1.1.1.1 0.0.0.0

bgp 200
router-id 1.1.1.1
pe 2.2.2.2 as 200
pe 2.2.2.2 con loo0
pe 3.3.3.3 as 200
pe 3.3.3.3 con loo0

2、R2的配置

sys
un in en
sys R2
int g0/0/0
ip add 10.0.12.2 24
int g0/0/1
ip add 10.0.24.2 24
int loo0
ip add 2.2.2.2 32

ospf 1 router-id 2.2.2.2
area 0
net 2.2.2.2 0.0.0.0
net 10.0.12.0 0.0.0.255

bgp 200
router-id 2.2.2.2
pe 1.1.1.1 as 200
pe 1.1.1.1 con loo0
pe 1.1.1.1 next-hop-local
pe 3.3.3.3 as 200
pe 3.3.3.3 con loo0
pe 3.3.3.3 next-hop-local
pe 10.0.24.4 as 100
net 2.2.2.2 32
net 1.1.1.1 32

3、R3的配置

sys
un in en
sys R3
int g0/0/1
ip add 10.0.13.3 24
int g0/0/0
ip add 10.0.35.3 24
int loo0
ip add 3.3.3.3  32

ospf 1 router-id 3.3.3.3
area 0
net 10.0.13.0 0.0.0.255
net 3.3.3.3 0.0.0.0

ip ip-prefix R1_to_45 index 10 permit 10.0.45.0 24
route-policy R1_to_45 permit node 10
if-match ip-prefix R1_to_45
apply local-preference 200

route-policy R1_to_45 permit node 20

bgp 200
router-id 3.3.3.3
pe 1.1.1.1 as 200
pe 1.1.1.1 con loo0
pe 1.1.1.1 next-hop-local
peer 1.1.1.1 route-policy R1_to_45 export
pe 2.2.2.2 as 200
pe 2.2.2.2 con loo0
pe 2.2.2.2 next-hop-local
pe 10.0.35.5 as 300
net 3.3.3.3 32
net 1.1.1.1 32

4、R4的配置

sys
un in en
sys R4
int g0/0/1
ip add 10.0.24.4 24
int g0/0/2
ip add 10.0.45.4 24
int g0/0/3
ip add 10.0.54.4 24
int loo0
ip add 4.4.4.4 32

acl number 2000
rule 1 permit source 4.4.4.4 0
rule 2 permit source 10.0.45.0 0.0.0.255
rule 3 permit source 10.0.54.0 0.0.0.255

route-policy 1 permit node 1
if-match acl 2000

bgp 100
router-id 4.4.4.4
pe 10.0.24.2 as 200
pe 10.0.45.5 as 300
pe 10.0.54.5 as 300
import-route direct route-policy 1

5、R5的配置

sys
un in en
sys R5
int g0/0/0
ip add 10.0.35.5 24
int g0/0/2
ip add 10.0.45.5 24
int g0/0/3
ip add 10.0.54.5 24
int loo0
ip add 5.5.5.5 32

acl number 2000
rule 1 permit source 5.5.5.5 0
rule 2 permit source 10.0.45.0 0.0.0.255
rule 3 permit source 10.0.54.0 0.0.0.255

route-policy 1 permit node 1
if-match acl 2000

bgp 300
router-id 5.5.5.5
pe 10.0.45.4 as 100
pe 10.0.54.4 as 100
pe 10.0.35.3 as 200
import-route direct route-policy 1

四、实验结果

1、在R1上查看去往10.0.45.0的BGP路由条目，与去往10.0.54.0对比

• 默认情况下，BGP会优选从Router-ID小的设备走。