华为AR2220 在AS内local-pref影响对端设备选路（local-pref仅在IBGP邻居之间有效）

骑猪看日落 2023-07-22 12:26 4阅读 0赞

## 一、网络拓扑 ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RsYWRhZ2lv_size_16_color_FFFFFF_t_70][]

需求：AR1默认选择路线是AR1 > AR2 > AR4到200.1.1.1（AR2 route-id小），但是链路带宽低。现在希望在AS65008内仅改变AR3的local-pre值，实现选择高带宽链路，路线访问：AR1 > AR3 > AR4 到200.1.1.1

*  Local\_Pref属性仅在IBGP邻居之间有效，不通告给其他AS。它表明路由器的BGP优先级，值越大越优。
 *  Local\_Pref属性用于判断流量离开AS时的最佳路由。当BGP路由器通过不同的IBGP邻居获得目的地址相同但下一跳不同的多条路由时，将优先选择Local\_Pref属性值较高的路由，其默认值为100。
 *  在AR3上做Local\_Pref配置，将策略应用在对AR1发布路由的export方向，从而影响AR1的选路。（因为有Preference\_Value方法，可以直接在AR1上做配置，从而影响AR1的选路，在另外一篇文章介绍）

## 二、基本配置 ##

1、AR1

1、配置接口
    <Huawei>system-view
    [Huawei]sysname AR1
    [AR1]interface  GigabitEthernet  0/0/0
    [AR1-GigabitEthernet0/0/0]ip address  10.1.12.1 24	
    [AR1-GigabitEthernet0/0/0]quit
    [AR1]interface  GigabitEthernet  0/0/1
    [AR1-GigabitEthernet0/0/1]ip address  10.1.13.1 24
    [AR1-GigabitEthernet0/0/1]quit
    [AR1]interface  LoopBack  0
    [AR1-LoopBack0]ip address  1.1.1.1 32
    [AR1-LoopBack0]quit
    
    2、配置OSPF
    [AR1]ospf 1 router-id 1.1.1.1
    [AR1-ospf-1]area 0
    [AR1-ospf-1-area-0.0.0.0]network  10.1.12.0 0.0.0.255
    [AR1-ospf-1-area-0.0.0.0]network  10.1.13.0 0.0.0.255
    [AR1-ospf-1-area-0.0.0.0]quit	
    [AR1-ospf-1]import-route direct
    [AR1-ospf-1]quit
    
    3、配置IBGP
    [AR1]bgp 65008
    [AR1-bgp]router-id 1.1.1.1
    [AR1-bgp]peer 10.1.12.2 as-number 65008
    [AR1-bgp]peer 10.1.13.3 as-number 65008	
    [AR1-bgp]import-route ospf 1
    [AR1-bgp]quit

2、AR2

1、配置接口
    <Huawei>system-view 
    [Huawei]sysname AR2
    [AR2]interface  LoopBack 0
    [AR2-LoopBack0]ip address  2.2.2.2 32
    [AR2-LoopBack0]quit
    [AR2]interface GigabitEthernet 0/0/0
    [AR2-GigabitEthernet0/0/0]ip address 10.1.12.2 24	
    [AR2-GigabitEthernet0/0/0]quit
    [AR2]interface  GigabitEthernet  0/0/2
    [AR2-GigabitEthernet0/0/2]ip address  10.1.24.2 24
    [AR2-GigabitEthernet0/0/2]quit
    
    2、配置OSPF
    [AR2]ospf 1 router-id  2.2.2.2
    [AR2-ospf-1]area 0
    [AR2-ospf-1-area-0.0.0.0]network  10.1.12.0 0.0.0.255
    [AR2-ospf-1]import-route direct
    [AR2-ospf-1]quit 
    
    3、配置BGP
    [AR2]bgp 65008
    [AR2-bgp]router-id 2.2.2.2
    [AR2-bgp]peer 10.1.12.1 as-number 65008        #IBGP
    [AR2-bgp]peer 10.1.24.4 as-number 65009	       #EBGP
    [AR2-bgp]import-route ospf 1
    [AR2-bgp]quit

3、AR3

1、配置接口
    <Huawei>system-view
    [Huawei]sysname AR3	
    [AR3]interface  GigabitEthernet  0/0/1
    [AR3-GigabitEthernet0/0/1]ip address  10.1.13.3 24	
    [AR3-GigabitEthernet0/0/1]quit
    [AR3]interface  GigabitEthernet  0/0/0
    [AR3-GigabitEthernet0/0/0]ip address  10.1.34.3 24	
    [AR3-GigabitEthernet0/0/0]quit
    [AR3]interface  LoopBack  0
    [AR3-LoopBack0]ip address  3.3.3.3 32
    [AR3-LoopBack0]quit
    
    2、配置OSPF
    [AR3]ospf 1 router-id 3.3.3.3
    [AR3-ospf-1]area 0
    [AR3-ospf-1-area-0.0.0.0]network  10.1.13.0 0.0.0.255	
    [AR3-ospf-1-area-0.0.0.0]quit
    [AR3-ospf-1]import-route direct
    [AR3-ospf-1]quit
    
    3、配置BGP
    [AR3]bgp 65008
    [AR3-bgp]router-id 3.3.3.3
    [AR3-bgp]peer 10.1.13.1 as-number 65008
    [AR3-bgp]peer 10.1.34.4 as-number 65009
    [AR3-bgp]import-route ospf  1
    [AR3-bgp]quit

4、AR4

1、配置接口
    <Huawei>system-view
    [Huawei]sysname AR4
    [AR4]interface  GigabitEthernet  0/0/2
    [AR4-GigabitEthernet0/0/2]ip address  10.1.24.4 24	
    [AR4-GigabitEthernet0/0/2]quit	
    [AR4]interface  GigabitEthernet  0/0/0
    [AR4-GigabitEthernet0/0/0]ip address  10.1.34.4 24	
    [AR4-GigabitEthernet0/0/0]quit
    [AR4]interface  LoopBack  0
    [AR4-LoopBack0]ip address  4.4.4.4 32
    [AR4-LoopBack0]quit
    [AR4]interface  LoopBack  1
    [AR4-LoopBack1]ip address  200.1.1.1 24
    [AR4-LoopBack1]quit
    [AR4]interface  LoopBack  2
    [AR4-LoopBack2]ip address  200.1.2.1 24
    [AR4-LoopBack2]quit
    
    2、配置BGP
    [AR4]bgp 65009
    [AR4-bgp]peer 10.1.24.2 as-number 65008
    [AR4-bgp]peer 10.1.34.3 as-number 65008
    [AR4-bgp]import-route direct
    [AR4-bgp]quit

5、查看BGP路由表

<AR1>tracert 200.1.1.1
    
     traceroute to  200.1.1.1(200.1.1.1), max hops: 30 ,packet length: 40,press CTRL_C to break 
    
     1 10.1.12.2 30 ms  30 ms  10 ms 
    
     2 10.1.24.4 20 ms  20 ms  20 ms 
    <AR1>tracert 200.1.2.1
    
     traceroute to  200.1.2.1(200.1.2.1), max hops: 30 ,packet length: 40,press CTRL_C to break 
    
     1 10.1.12.2 30 ms  30 ms  20 ms 
    
     2 10.1.24.4 20 ms  20 ms  30 ms

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RsYWRhZ2lv_size_16_color_FFFFFF_t_70 1][]

## 三、全部目的地址改变线路 ##

1、修改local-preference值，默认为100（越大越优先）

[AR3]bgp 65008
    [AR3-bgp]ipv4-family unicast
    [AR3-bgp-af-ipv4]default local-preference 200
    [AR3-bgp-af-ipv4]return

2、查看BGP路由表，线路已经被改变

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RsYWRhZ2lv_size_16_color_FFFFFF_t_70 2][]

3、跟踪路由确认

<AR1>tracert 200.1.1.1
    
     traceroute to  200.1.1.1(200.1.1.1), max hops: 30 ,packet length: 40,press CTRL_C to break 
    
     1 10.1.13.3 30 ms  20 ms  20 ms 
    
     2 10.1.34.4 20 ms  20 ms  30 ms 
    <AR1>tracert 200.1.2.1
    
     traceroute to  200.1.2.1(200.1.2.1), max hops: 30 ,packet length: 40,press CTRL_C to break 
    
     1 10.1.13.3 30 ms  20 ms  10 ms 
    
     2 10.1.34.4 30 ms  20 ms  20 ms

## 四、部分目的地址改变线路 ##

1、修改BGP的Local\_Preference，将策略应用在对AR1发布路由的export方向

[AR3]bgp 65008
    [AR3-bgp]undo default local-preference	
    [AR3-bgp]ipv4-family unicast
    [AR3-bgp-af-ipv4]peer 10.1.13.1 route-policy local-pre export 	
    [AR3-bgp-af-ipv4]return

2、定义路由策略

[AR3]route-policy local-pre permit node 10
    [AR3-route-policy]if-match ip-prefix local-pre
    [AR3-route-policy]apply local-preference 200
    [AR3-route-policy]quit

3、创建IPv4地址前缀列表

[AR3]ip ip-prefix local-pre index 10 permit 200.1.1.0 24

4、查看BGP路由表

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RsYWRhZ2lv_size_16_color_FFFFFF_t_70 3][]

5、跟踪路由测试（200.1.1.1线路已经被改变，200.1.2.1使用默认线路）

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RsYWRhZ2lv_size_16_color_FFFFFF_t_70 4][]

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