配置GRE over IPv4示例（静态路由）

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组网需求

  1. Router A、Router B、Router C使用OSPF协议路由可达
  2. 需要在Router A与Router C之间建立直连链路（部署GRE隧道）
  3. 通过静态路由指定到达对端的报文通过Tunnel接口转发，实现PC1与PC2可以互相通信
  4. PC1和PC2分别指定Router A、Router C为自己的缺省网关

组网拓扑

GRE over IPv4示例拓扑图

配置思路

  1. 各路由器之间配置OSPF协议实现互联互通
  2. 在Router A和Router C之间创建Tunnel接口，配置GRE隧道，指点Tunnel的源地址和目的地址，使报文封装后通过OSPF路由转发
  3. Tunnel的源地址为发出报文的物理接口的IP地址，目的地址为接收报文的物理接口的IP地址
  4. PC1与PC2之间的流量通过GRE隧道传输，Router A与Router C上配置静态路由
  5. 以对端PC所在网段为目的地址，出接口为本端配置的Tunnel接口

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 20.1.1.1 30
      int g0/0/2
        ip add 10.1.1.1 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 20.1.1.2 30
    int g0/0/1
      ip add 30.1.1.1 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 30.1.1.2 30
    int g0/0/2
      ip add 10.2.1.1 30
    int LoopBack 0
      ip add 3.3.3.3 32

  1. 配置OSPF协议

    • Router A配置

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      ospf 1 router-id 1.1.1.1
        area 0
          network 20.1.1.0 0.0.0.3

  • Router B配置

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    ospf 1 router-id 2.2.2.2
      area 0
        network 20.1.1.0 0.0.0.3
        network 30.1.1.0 0.0.0.3

  • Router C配置

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    ospf 1 router-id 3.3.3.3
      area 0
        network 30.1.1.0 0.0.0.3

  1. 配置Tunnel接口（接口协议为GRE、接口IP地址、源地址、目的地址）

    • Router A配置

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      int Tunnel 0/0/0
        tunnel-protocol gre
        ip add 40.1.1.1 30
        source 20.1.1.1
        destination 30.1.1.1

  • Router C配置

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    int Tunnel 0/0/0
      tunnel-protocol gre
      ip add 40.1.1.2 30
      source 30.1.1.1
      destination 20.1.1.1

  1. 配置静态路由

    • Router A配置

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      ip route-static 10.2.1.0 30 Tunnel 0/0/0

  • Router C配置

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    ip route-static 10.1.1.0 30 Tunnel 0/0/0

查看结果

  1. 查看OSPF路由表

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    display ip routing-table protocol ospf

    <Router A>display ip routing-table protocol ospf
    Route Flags: R - relay, D - download to fib
    ------------------------------------------------------------------------------
    Public routing table : OSPF
             Destinations : 1        Routes : 1        

    OSPF routing table status : <Active>
             Destinations : 1        Routes : 1

    Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface

           30.1.1.0/30  OSPF    10   2           D   20.1.1.2        GigabitEthernet
    0/0/0

    OSPF routing table status : <Inactive>
             Destinations : 0        Routes : 0

  1. 查看Tunnel隧道是否建立成功

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    ping -a 40.1.1.1 40.1.1.2

    <Router A>ping -a 40.1.1.1 40.1.1.2
      PING 40.1.1.2: 56  data bytes, press CTRL_C to break
        Reply from 40.1.1.2: bytes=56 Sequence=1 ttl=255 time=20 ms
        Reply from 40.1.1.2: bytes=56 Sequence=2 ttl=255 time=20 ms
        Reply from 40.1.1.2: bytes=56 Sequence=3 ttl=255 time=20 ms
        Reply from 40.1.1.2: bytes=56 Sequence=4 ttl=255 time=20 ms
        Reply from 40.1.1.2: bytes=56 Sequence=5 ttl=255 time=30 ms

      --- 40.1.1.2 ping statistics ---
        5 packet(s) transmitted
        5 packet(s) received
        0.00% packet loss
        round-trip min/avg/max = 20/22/30 ms

  1. 查看到目的地址10.2.1.2 的路由表

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    display ip routing-table 10.2.1.2

    <Router A>display ip routing-table 10.2.1.2
    Route Flags: R - relay, D - download to fib
    ------------------------------------------------------------------------------
    Routing Table : Public
    Summary Count : 1
    Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface

           10.2.1.0/30  Static  60   0           D   40.1.1.1        Tunnel0/0/0

  1. ping和trace地址

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    ping 10.2.1.2
    tracert 10.2.1.2

    PC>ping 10.2.1.2

    Ping 10.2.1.2: 32 data bytes, Press Ctrl_C to break
    Request timeout!
    From 10.2.1.2: bytes=32 seq=2 ttl=126 time=31 ms
    From 10.2.1.2: bytes=32 seq=3 ttl=126 time=32 ms
    From 10.2.1.2: bytes=32 seq=4 ttl=126 time=31 ms
    From 10.2.1.2: bytes=32 seq=5 ttl=126 time=15 ms

    --- 10.2.1.2 ping statistics ---
      5 packet(s) transmitted
      4 packet(s) received
      20.00% packet loss
      round-trip min/avg/max = 0/27/32 ms

    PC>tracert 10.2.1.2

    traceroute to 10.2.1.2, 8 hops max
    (ICMP), press Ctrl+C to stop
     1  10.1.1.1   16 ms  <1 ms  15 ms
     2  40.1.1.2   16 ms  31 ms  32 ms
     3  10.2.1.2   15 ms  31 ms  16 ms
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