45、BGP配置实验之Local preference选路

1、Local preference选路解析

属性
传播范围
默认值
优先值 方向
备注
weight 本路由器 本路由器32768,其他路由器0 大值优先 IN CISCO私有

Local preference AS内部 100:边界路由器,通告给IBGP邻居,告知如何离开本AS 大值优先 OUT

45、BGP配置实验之Local preference选路

修改Local preference值的方法:

方法一:全部修改通告给IBGP邻居的路由的Local preference值,例如:

router bgp 4

 bgp default local-preference 125

方法二:部分修改通告给IBGP邻居的路由的Local preference值,例如:



2、实验拓扑

45、BGP配置实验之Local preference选路3、基础配置

R1配置

interface Loopback0

 ip address 1.1.1.1 255.255.255.0

interface Serial0/0

 ip address 13.1.1.1 255.255.255.0

interface Serial0/1

 ip address 14.1.1.1 255.255.255.0

router ospf 110

 router-id 1.1.1.1

 log-adjacency-changes

 network 1.1.1.0 0.0.0.255 area 0

 network 14.1.1.0 0.0.0.255 area 0

router bgp 4

 no synchronization

 bgp router-id 1.1.1.1

 neighbor 4.4.4.4 remote-as 4

 neighbor 4.4.4.4 update-source Loopback0

 neighbor 4.4.4.4 next-hop-self

 neighbor 13.1.1.3 remote-as 3

 no auto-summary


R2配置

interface Loopback0

 ip address 2.2.2.2 255.255.255.0

interface Serial0/1

 ip address 23.1.1.2 255.255.255.0

interface FastEthernet1/0

 ip address 24.1.1.2 255.255.255.0

router ospf 110

 router-id 2.2.2.2

 network 2.2.2.0 0.0.0.255 area 0

 network 24.1.1.0 0.0.0.255 area 0

router bgp 4

 no synchronization

 bgp router-id 2.2.2.2

 neighbor 4.4.4.4 remote-as 4

 neighbor 4.4.4.4 update-source Loopback0

 neighbor 4.4.4.4 next-hop-self

 neighbor 23.1.1.3 remote-as 3

 no auto-summary


R3配置

interface Loopback0

 ip address 3.3.3.3 255.255.255.0

interface Loopback1

 ip address 33.33.33.33 255.255.255.0        

interface Serial0/0

 ip address 13.1.1.3 255.255.255.0

interface Serial0/1

 ip address 23.1.1.3 255.255.255.0router bgp 3

 no synchronization

 bgp router-id 3.3.3.3

 network 3.3.3.0 mask 255.255.255.0

 network 33.33.33.0 mask 255.255.255.0

 neighbor 13.1.1.1 remote-as 4

 neighbor 23.1.1.2 remote-as 4

 no auto-summary


R4配置

interface Loopback0

 ip address 4.4.4.4 255.255.255.0

interface Serial0/1

 ip address 14.1.1.4 255.255.255.0

interface FastEthernet1/0

 ip address 24.1.1.4 255.255.255.0

router ospf 110

 router-id 4.4.4.4

 network 4.4.4.0 0.0.0.255 area 0

 network 14.1.1.0 0.0.0.255 area 0

 network 24.1.1.0 0.0.0.255 area 0

router bgp 4

 no synchronization

 bgp router-id 4.4.4.4

 neighbor 1.1.1.1 remote-as 4

 neighbor 1.1.1.1 update-source Loopback0

 neighbor 2.2.2.2 remote-as 4

 neighbor 2.2.2.2 update-source Loopback0

 no auto-summary


4、默认选路

45、BGP配置实验之Local preference选路根据BGP选路原则第八条可以知道,R4到达3.3.3.0/24、33.33.33.0/24都是经过R2。

45、BGP配置实验之Local preference选路

45、BGP配置实验之Local preference选路


5、全部修改通告给IBGP邻居的路由的Local preference值

由前面可以R4到达3.3.3.0/24、33.33.33.0/24都是经过R2,我们通过修改Local preference值将R4到达3.3.3.0/24、33.33.33.0/24都是经过R1。

R4配置

router bgp 4

 bgp default local-preference 125

45、BGP配置实验之Local preference选路


6、部分修改通告给IBGP邻居的路由的Local preference值

R4到达3.3.3.0/24、33.33.33.0/24都是经过R2,我们通过修改Local preference值将R4到达3.3.3.0/24经过R2、达到33.33.33.0/24都是经过R1。

R4配置

ip prefix-list 1 seq 5 permit 33.33.33.0/24

no cdp log mismatch duplex

route-map L permit 10

 match ip address prefix-list 1

 set local-preference 125

route-map L permit 20

router bgp 4

 neighbor 4.4.4.4 route-map L out

45、BGP配置实验之Local preference选路







      本文转自开源殿堂 51CTO博客,原文链接:http://blog.51cto.com/kaiyuandiantang/1722005,如需转载请自行联系原作者