loopback-detection 打不开？

1.5  环路检测典型配置举例

1. 组网需求

·     三台设备Device A、Device B和Device C组成一个物理上的环形网络。

·     通过在Device A上配置环路检测功能，使系统能够自动关闭Device A上出现环路的端口，并通过打印日志信息来通知用户检查网络。

2. 组网图

图1-3 环路检测典型组网图

3. 配置步骤

(1)     配置Device A

# 创建VLAN 100，并全局使能该VLAN内的环路检测功能。

<DeviceA> system-view

[DeviceA] vlan 100

[DeviceA–vlan100] quit

[DeviceA] loopback-detection global enable vlan 100

# 配置端口Ten-GigabitEthernet1/0/1和Ten-GigabitEthernet1/0/2为Trunk类型，并允许VLAN 100通过。

[DeviceA] interface ten-gigabitethernet 1/0/1

[DeviceA-Ten-GigabitEthernet1/0/1] port link-type trunk

[DeviceA-Ten-GigabitEthernet1/0/1] port trunk permit vlan 100

[DeviceA-Ten-GigabitEthernet1/0/1] quit

[DeviceA] interface ten-gigabitethernet 1/0/2

[DeviceA-Ten-GigabitEthernet1/0/2] port link-type trunk

[DeviceA-Ten-GigabitEthernet1/0/2] port trunk permit vlan 100

[DeviceA-Ten-GigabitEthernet1/0/2] quit

# 全局配置环路检测的处理模式为Shutdown模式。

[DeviceA] loopback-detection global action shutdown

# 配置环路检测的时间间隔为35秒。

[DeviceA] loopback-detection interval-time 35

(2)     配置Device B

# 创建VLAN 100。

<DeviceB> system-view

[DeviceB] vlan 100

[DeviceB–vlan100] quit

# 配置端口Ten-GigabitEthernet1/0/1和Ten-GigabitEthernet1/0/2为Trunk类型，并允许VLAN 100通过。

[DeviceB] interface ten-gigabitethernet 1/0/1

[DeviceB-Ten-GigabitEthernet1/0/1] port link-type trunk

[DeviceB-Ten-GigabitEthernet1/0/1] port trunk permit vlan 100

[DeviceB-Ten-GigabitEthernet1/0/1] quit

[DeviceB] interface ten-gigabitethernet 1/0/2

[DeviceB-Ten-GigabitEthernet1/0/2] port link-type trunk

[DeviceB-Ten-GigabitEthernet1/0/2] port trunk permit vlan 100

[DeviceB-Ten-GigabitEthernet1/0/2] quit

(3)     配置Device C

# 创建VLAN 100。

<DeviceC> system-view

[DeviceC] vlan 100

[DeviceC–vlan100] quit

# 配置端口Ten-GigabitEthernet1/0/1和Ten-GigabitEthernet1/0/2为Trunk类型，并允许VLAN 100通过。

[DeviceC] interface ten-gigabitethernet 1/0/1

[DeviceC-Ten-GigabitEthernet1/0/1] port link-type trunk

[DeviceC-Ten-GigabitEthernet1/0/1] port trunk permit vlan 100

[DeviceC-Ten-GigabitEthernet1/0/1] quit

[DeviceC] interface ten-gigabitethernet 1/0/2

[DeviceC-Ten-GigabitEthernet1/0/2] port link-type trunk

[DeviceC-Ten-GigabitEthernet1/0/2] port trunk permit vlan 100

[DeviceC-Ten-GigabitEthernet1/0/2] quit

4. 验证配置

当配置完成后，系统在一个环路检测时间间隔内在Device A的端口Ten-GigabitEthernet1/0/1和Ten-GigabitEthernet1/0/2上都检测到了环路，于是将这两个端口自动关闭，并打印了如下日志信息：

[DeviceA]

%Feb 24 15:04:29:663 2013 DeviceA LPDT/4/LPDT_LOOPED: Loopback exists on Ten-GigabitEthernet1/0/1.

%Feb 24 15:04:29:667 2013 DeviceA LPDT/4/LPDT_LOOPED: Loopback exists on Ten-GigabitEthernet1/0/2.

%Feb 24 15:04:44:243 2013 DeviceA LPDT/5/LPDT_RECOVERED: Loopback on Ten-GigabitEthernet1/0/1 recovered.

%Feb 24 15:04:44:248 2013 DeviceA LPDT/5/LPDT_RECOVERED: Loopback on Ten-GigabitEthernet1/0/2 recovered.

使用display loopback-detection命令可以查看Device A上环路检测的配置和运行情况：

# 显示Device A上环路检测的配置和运行情况。

[DeviceA] display loopback-detection

Loopback detection is enabled.

Loopback detection interval is 35 second(s).

No loopback is detected.

由此可见，Device A上并未显示在端口Ten-GigabitEthernet1/0/1和Ten-GigabitEthernet1/0/2上检测到环路，这是由于环路检测功能运行在Shutdown模式下，端口Ten-GigabitEthernet1/0/1和Ten-GigabitEthernet1/0/2上出现环路后均已被自动关闭，因此这两个端口上的环路已消除。此时，使用display interface命令分别查看Device A上端口Ten-GigabitEthernet1/0/1和Ten-GigabitEthernet1/0/2的状态信息：

# 显示Device A上端口Ten-GigabitEthernet1/0/1的状态信息。

[DeviceA] display interface ten-gigabitethernet 1/0/1

Ten-GigabitEthernet1/0/1 current state: DOWN (Loopback detection down)

...

# 显示Device A上端口Ten-GigabitEthernet1/0/2的状态信息。

[DeviceA] display interface ten-gigabitethernet 1/0/2

Ten-GigabitEthernet1/0/2 current state: DOWN (Loopback detection down)

...

由此可见，端口Ten-GigabitEthernet1/0/1和Ten-GigabitEthernet1/0/2均已被环路检测模块自动关闭。