BGP与BFD联动示例

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组网需求

  1. Router A属于AS 100，Router B和Router C属于AS 200
  2. Router A与Router B、Router C建立非直连EBGP连接
  3. 主链路为：Router A->Router B，备份链路：Router A->Router C->Router B
  4. 要求：快速感知故障，使得主链路快速切换到备用链路

组网拓扑

BGP与BFD联动拓扑图

配置思路

  1. 各路由器上配置BGP基本功能
  2. 配置MED属性控制路由的选路功能
  3. 在Router A和Router B上使能BFD检测机制

配置命令

  1. 配置路由器基本功能以及各个接口地址

    • Router A配置

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      sys
      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
    sys Router B
    int g0/0/0
      ip add 200.1.1.2 30
    int g0/0/2
      ip add 9.1.1.1 30
    int LoopBack 0
      ip add 2.2.2.2 32
    int LoopBack 1
      ip add 172.16.1.1 32

  • Router C 配置

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    sys
    sys Router C
    int g0/0/1
      ip add 200.1.2.2 30
    int g0/0/2
      ip add 9.1.1.2 30
    int LoopBack 0
      ip add 3.3.3.3 32

  1. 配置非直连EBGP以及IBGP

    • Router A配置

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      sys
      bgp 100
        router-id 1.1.1.1
        peer 200.1.1.2 as-number 200
        peer 200.1.1.2 ebgp-max-hop
        peer 200.1.2.2 as-number 200
        peer 200.1.2.2 ebgp-max-hop

  • Router B配置

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    bgp 200
      router-id 2.2.2.2
      peer 200.1.1.1 as-numebr 100
      peer 200.1.1.1 ebgp-max-hop
      peer 9.1.1.2 as-number 200

  • Router C配置

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    sys
    bgp 200
      router-id 3.3.3.3
      peer 200.1.2.1 as-number 100
      peer 200.1.2.1 as-number 100
      peer 9.1.1.1 as-number 200

  1. 宣告路由

    • Router B配置

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      sys
      bgp 200
        ipv4-family unicast
          network 172.16.1.1 32

  1. 配置MED属性，形成主备链路

    • Router B配置

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      sys
      route-policy BGP_MED permit node 10
        apply cost 100
      bgp 200
        ipv4-family unicast
          peer 200.1.1.1 route-policy BGP_MED export

  • Router C配置

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    sys
    route-policy BGP_MED permit node 10
      apply cost 150
    bgp 200
      ipv4-family unicast
        peer 200.1.2.1 route-policy BGP_MED export
  1. 配置BGP与BFD联动

查看结果

  1. 配置非直连EBGP以及IGP之后的邻居表

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    display bgp peer

    <Router A>dis bgp peer

     BGP local router ID : 1.1.1.1
     Local AS number : 100
     Total number of peers : 2		  Peers in established state : 2

      Peer            V          AS  MsgRcvd  MsgSent  OutQ  Up/Down       State Pre
    fRcv

      200.1.1.2       4         200       18       19     0 00:15:23 Established    
       1
      200.1.2.2       4         200       34       37     0 00:31:59 Established    
       1

  1. 宣告完路由后的路由表

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    display bgp routing-table

    <Router A>dis bgp routing-table

     BGP Local router ID is 1.1.1.1 
     Status codes: * - valid, > - best, d - damped,
                   h - history,  i - internal, s - suppressed, S - Stale
                   Origin : i - IGP, e - EGP, ? - incomplete


     Total Number of Routes: 2
          Network            NextHop        MED        LocPrf    PrefVal Path/Ogn

     *>   172.16.1.0/32      200.1.1.2       0                     0      200i
     *                       200.1.2.2                             0      200i

  1. 配置MED属性后的路由表

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    disply bgp routong-table 
    <Router A>dis bgp routing-table

     BGP Local router ID is 1.1.1.1 
     Status codes: * - valid, > - best, d - damped,
                   h - history,  i - internal, s - suppressed, S - Stale
                   Origin : i - IGP, e - EGP, ? - incomplete


     Total Number of Routes: 2
          Network            NextHop        MED        LocPrf    PrefVal Path/Ogn

     *>   172.16.1.0/32      200.1.1.2       100                   0      200i
     *                       200.1.2.2       150                   0      200i

  1. 配置BGP与BFD联动后，BFD的session表

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    dispaly bgp bfd session all

    <Router A>dis bgp bfd session all
      Local_Address      Peer_Address       LD/RD       Interface
      200.1.1.1          200.1.1.2          8193/8193   GigabitEthernet0/0/0
      Tx-interval(ms)    Rx-interval(ms)    Multiplier  Session-State
      100                100                4           Up                  
      Wtr-interval(m)
      0

  1. 模拟端口down，报障信息以及BGP路由表变化

    • 报障信息

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      [Router B-GigabitEthernet0/0/0]
      Mar 29 2022 21:34:14-08:00 Router B %%01IFPDT/4/IF_STATE(l)[0]:Interface Gigabit
      Ethernet0/0/0 has turned into DOWN state.
      [Router B-GigabitEthernet0/0/0]
      Mar 29 2022 21:34:14-08:00 Router B %%01BFD/4/STACHG_TODWN(l)[1]:BFD session cha
      nged to Down. (SlotNumber=0, Discriminator=18874368, Diagnostic=DetectDown, Appl
      ications=BGP, ProcessPST=False, BindInterfaceName=GigabitEthernet0/0/0, Interfac
      ePhysicalState=Up, InterfaceProtocolState=Up) 
      [Router B-GigabitEthernet0/0/0]
      Mar 29 2022 21:34:14-08:00 Router B %%01BGP/3/STATE_CHG_UPDOWN(l)[2]:The status 
      of the peer 200.1.1.1 changed from ESTABLISHED to IDLE. (InstanceName=Public, St
      ateChangeReason=CEASE/BFD Session Down)  
      [Router B-GigabitEthernet0/0/0]
      Mar 29 2022 21:34:14-08:00 Router B %%01IFNET/4/LINK_STATE(l)[3]:The line protoc
      ol IP on the interface GigabitEthernet0/0/0 has entered the DOWN state. 
      [Router B-GigabitEthernet0/0/0]

  • BGP路由表变化

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    display bgp routing-table

    <Router A>dis bgp routing-table

     BGP Local router ID is 1.1.1.1 
     Status codes: * - valid, > - best, d - damped,
                   h - history,  i - internal, s - suppressed, S - Stale
                   Origin : i - IGP, e - EGP, ? - incomplete


     Total Number of Routes: 1
          Network            NextHop        MED        LocPrf    PrefVal Path/Ogn

     *>   172.16.1.0/32      200.1.2.2       150                   0      200i
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