BGP负载分担示例

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组网需求

  1. 所有路由器配置BGP，Router A在AS 100，Router B、Router C在AS 300，Router D在AS 200
  2. 要求：充分利用网络资源，减少Router A到8.1.1.1/32的网络阻塞

组网拓扑

BGP负载分担拓扑图

配置思路

  1. Router A与Router B、Router C之间配置EBGP，Router D与Router B、Router C之间配置EBGP
  2. 在Router A上配置负载分担功能，使得从Router A发送的流量可以经过Router B和Router C两条路径到Router D

配置命令

  1. 配置路由器基本功能以及各个接口IP地址

    • Router A配置

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      sys Router A
      int g0/0/0
        ip add 200.1.1.1 30
      int g0/0/1
        ip add 200.1.2.1 30
      int LoopBack 0
        ip add 1.1.1.1 32

  • Router B配置

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    sys Router B
    int g0/0/0
      ip add 200.1.1.2 30
    int g0/0/2
      ip add 200.1.3.2 30
    int LoopBack 0
      ip add 2.2.2.2 32

  • Router C配置

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    sys Router C
    int g0/0/1
      ip add 200.1.2.2 30
    int g0/0/2
      ip add 200.1.4.2 30
    int LoopBack 0
      ip add 3.3.3.3 32

  • Router D配置

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    sys Router D
    int g0/0/0
      ip add 200.1.3.1 30
    int g0/0/1
      ip add 200.1.4.1 30
    int g0/0/0
      ip add 4.4.4.4 32

  1. 配置EBGP

    • Router A配置

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      bgp 100
        router-id 1.1.1.1
        peer 200.1.1.2 as-number 300
        peer 200.1.2.2 as-number 300

  • Router B配置

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    bgp 300
      router-id 2.2.2.2
      peer 200.1.1.1 as-number 100
      peer 200.1.3.1 as-number 200

  • Router C配置

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    bgp 300
      router-id 3.3.3.3
      peer 200.1.2.1 as-number 100
      peer 200.1.4.1 as-number 200

  • Router D配置

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    bgp 200
      router-id 4.4.4.4
      peer 200.1.3.2 as-number 300
      peer 200.1.4.2 as-number 300

  1. 宣告网段

    • Router A配置

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      bgp 100
        ipv4-family unicast
          network 200.1.1.0 30
          network 200.1.2.0 30

  • Router B配置

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    bgp 300
      ipv4-family unicast
        network 200.1.1.0 30
        network 200.1.3.0 30

  • Router C配置

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    bgp 300
      ipv4-family unicast
        network 200.1.4.0 30
        network 200.1.2.0 30

  • Router D配置

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    sys
    bgp 200
      ipv4-family unicast
        network 200.1.3.0 30
        network 200.1.4.0 30
        network 8.1.1.1 32

  1. 配置负载均衡

    • Router A配置

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      bgp 100
        ipv4-family unicast
          maximum load-balancing 2

查看结果

  1. 没有配置负载均衡前Router A的路由表

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    display routing-table 8.1.1.1 32

    <Router A>dis bgp routing-table 8.1.1.1 32

     BGP local router ID : 1.1.1.1
     Local AS number : 100
         //一条路由被选
     Paths:   2 available, 1 best, 1 select
     BGP routing table entry information of 8.1.1.1/32:
     From: 200.1.1.2 (2.2.2.2)
     Route Duration: 00h05m25s  
     Direct Out-interface: GigabitEthernet0/0/0
     Original nexthop: 200.1.1.2
     Qos information : 0x0
     AS-path 300 200, origin igp, pref-val 0, valid, external, best, select, active,
     pre 255
         // 两个邻居都宣告
     Advertised to such 2 peers:
        200.1.1.2
        200.1.2.2
     BGP routing table entry information of 8.1.1.1/32:
     From: 200.1.2.2 (3.3.3.3)
     Route Duration: 00h05m19s  
     Direct Out-interface: GigabitEthernet0/0/1
     Original nexthop: 200.1.2.2
     Qos information : 0x0
     AS-path 300 200, origin igp, pref-val 0, valid, external, pre 255, not preferre
    d for router ID
     Not advertised to any peer yet

  1. 配置负载均衡后Router A的路由表

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    display routing-table 8.1.1.1 32

    <Router A>dis bgp routing-table 8.1.1.1 32

     BGP local router ID : 1.1.1.1
     Local AS number : 100
     // 两条路由被选
     Paths:   2 available, 1 best, 2 select
     BGP routing table entry information of 8.1.1.1/32:
     From: 200.1.1.2 (2.2.2.2)
     Route Duration: 00h11m45s  
     Direct Out-interface: GigabitEthernet0/0/0
     Original nexthop: 200.1.1.2
     Qos information : 0x0
     AS-path 300 200, origin igp, pref-val 0, valid, external, best, select, active,
     pre 255
     Advertised to such 2 peers:
        200.1.1.2
        200.1.2.2
     BGP routing table entry information of 8.1.1.1/32:
     From: 200.1.2.2 (3.3.3.3)
     Route Duration: 00h11m39s  
     Direct Out-interface: GigabitEthernet0/0/1
     Original nexthop: 200.1.2.2
     Qos information : 0x0
     AS-path 300 200, origin igp, pref-val 0, valid, external, select, active, pre 2
    55, not preferred for router ID
     Not advertised to any peer yet
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