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思科、华为、华三交换机的线缆检测功能

时间:2018-11-13 18:31:15      阅读:1484      评论:0      收藏:0      [点我收藏+]

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通俗地说线缆检测可以检测交换机接口到终端之间的网线情况。不管是思科还是华为、华三,在线缆检测时都使用了时域反射time domain reflectometer (TDR)技术。
通过时域反射TDR (Time Domain Reflectometry)检测电缆状态的原理如下:
交换机发送一个脉冲信号,脉冲信号在电缆中传输,如果遇到电缆末端或其它故障点,部分能量会被反射回来,这种现象称为时域反射。线缆检测技术就是测量脉冲在电缆中传输、达到故障点及返回的时间,把测量到的时间转换成距离。
华为和华三称之为虚电缆检测VCT(Virtual Cable Test)技术。

一、下面先以思科为例说一下:


测试环境一:思科3560-CG,一台8口千兆POE交换机


1、交叉线测试:

SDYC-UCDEMO_SW1#test cable-diagnostics tdr interface g0/8
TDR test started on interface Gi0/8
A TDR test can take a few seconds to run on an interface
Use ‘show cable-diagnostics tdr‘ to read the TDR results.
SDYC-UCDEMO_SW1#show cable-diagnostics tdr interface g0/8
TDR test last run on: March 30 02:30:30

Interface Speed Local pair Pair length Remote pair Pair status
Gi0/8 1000M Pair A 0 +/- 10 meters Pair B Normal
Pair B 0 +/- 10 meters Pair A Normal
Pair C 0 +/- 10 meters Pair C Normal
Pair D 0 +/- 10 meters Pair D Normal

2、直通线测试:

SDYC-UCDEMO_SW1#test cable-diagnostics tdr interface g0/8
TDR test started on interface Gi0/8
A TDR test can take a few seconds to run on an interface
Use ‘show cable-diagnostics tdr‘ to read the TDR results.

SDYC-UCDEMO_SW1#show cable-diagnostics tdr interface g0/8
TDR test last run on: March 30 02:32:09

Interface Speed Local pair Pair length Remote pair Pair status
Gi0/8 1000M Pair A 0 +/- 10 meters Pair B Normal
Pair B 0 +/- 10 meters Pair A Normal
Pair C 0 +/- 10 meters Pair D Normal
Pair D 0 +/- 10 meters Pair C Normal

3、错误线序测试:

SDYC-UCDEMO_SW1#test cable-diagnostics tdr interface g0/8
Link state may be affected during TDR test
TDR test started on interface Gi0/8
A TDR test can take a few seconds to run on an interface
Use ‘show cable-diagnostics tdr‘ to read the TDR results.

SDYC-UCDEMO_SW1#show cable-diagnostics tdr interface g0/8
TDR test last run on: March 30 02:34:36

Interface Speed Local pair Pair length Remote pair Pair status
Gi0/8 100M Pair A N/A Pair B Normal
Pair B N/A Pair A Normal
Pair C N/A Pair D Normal
Pair D N/A Pair C Normal
这条线的线序虽然是错的,但是是通的,所以后面显示的状态都是normal

4、线序超有问题的测试:

SDYC-UCDEMO_SW1#show cable-diagnostics tdr interface g0/8
TDR test last run on: March 30 03:06:38

Interface Speed Local pair Pair length Remote pair Pair status
Gi0/8 auto Pair A N/A N/A Normal
Pair B 0 +/- 10 meters N/A Short/Crosstalk
Pair C 0 +/- 10 meters N/A Open
Pair D N/A N/A Normal
这条线缆是线序超有问题的,接上去根本不通的,这时可以看到Pair Status上面显示的内容。


测试环境:一台2960XR交换机


1、直通线测试:

Switch#show cable-diagnostics tdr int g1/0/24
TDR test last run on: November 12 21:56:11

Interface Speed Local pair Pair length Remote pair Pair status
Gi1/0/24 1000M Pair A 22 +/- 10 meters Pair A Normal
Pair B 22 +/- 10 meters Pair B Normal
Pair C 22 +/- 10 meters Pair C Normal
Pair D 22 +/- 10 meters Pair D Normal
同一条网线,这个显示结果与3560-CG上有些不同。不过Pair的状态都是正常的。

2、交叉线测试:

Switch#test cable-dia tdr int g1/0/1
TDR test started on interface Gi1/0/1
A TDR test can take a few seconds to run on an interface
Use ‘show cable-diagnostics tdr‘ to read the TDR results.
Switch#show cable-diag tdr int g1/0/1
TDR test last run on: November 12 21:58:42

Interface Speed Local pair Pair length Remote pair Pair status
Gi1/0/1 1000M Pair A 21 +/- 10 meters Pair B Normal
Pair B 21 +/- 10 meters Pair A Normal
Pair C 21 +/- 10 meters Pair C Normal
Pair D 21 +/- 10 meters Pair D Normal

3、线序超有问题的线缆测试:

Switch#test cable-diagnostics tdr int g1/0/5
TDR test started on interface Gi1/0/5
A TDR test can take a few seconds to run on an interface
Use ‘show cable-diagnostics tdr‘ to read the TDR results.
Switch#show cable-diagnostics tdr int g1/0/5
TDR test last run on: November 12 22:03:52

Interface Speed Local pair Pair length Remote pair Pair status
Gi1/0/5 auto Pair A N/A N/A Normal
Pair B N/A N/A Normal
Pair C 1 +/- 10 meters N/A Open
Pair D 0 +/- 10 meters N/A Open

虽然这个也与3560-CG上显示的不同,不过都可以看出来这条线缆是有问题的。

技术分享图片
技术分享图片

需要说明一点,当我们进行TDR测试时,会影响到这条链路数据的传输,也就是说会导致该条线缆连接的客户端或是设备断网。
另外,它不支持对SFP口进行测试。

二、华为VCT测试

由于手头没有测试设备,下面的命令是查看文档所得
测试方法在接口模式下输入virtual-cable-test,如下所示:
技术分享图片
相关输出的说明如下:
技术分享图片

三、H3C的VCT测试

测试方法同华为一样,在接口模式下输入virtual-cable-test
显示结果如下:
技术分享图片
相关输出解释如下:
技术分享图片

在这里需要补充一下,这三家并不是所有的交换机都支持VCT,如果需要请查看相关文档。

还有就是这三家的VCT都只是针对网线的测试,不要用来测试光缆!

思科、华为、华三交换机的线缆检测功能

标签:ges   状态   run   tar   interface   一个   分享图片   dea   oss   

原文地址:http://blog.51cto.com/05wylz/2316522

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