Friday, February 10, 2012

Resolving layer 1 issues

Often times we have issues with cabling and don't know how to prove it. Fortunately if you are using Cisco switches you are in luck since there is a way to test the cabling using commands in the Cisco switches. Please not that this will bring that interface down, and is not recommended to be done during production hours.....
 As can see from the log below:

3d00h: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down
3d00h: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down
3d00h: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to down
3d00h: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to up
3d00h: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up
3d00h: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to up


How do we do that you ask? Well here goes:

Test_Switch01#test cable-diagnostics tdr interface GigabitEthernet0/1


To see the results:

Test_Switch01#sh cable-diagnostics tdr int gigabitEthernet 0/1
TDR test last run on: March 04 00:36:40

Interface Speed        Local pair         Pair         length               Remote pair        Pair status
--------- ----- ---------- ------------------ -----------            -------------         -------
Gi0/1      100M               Pair    A       0            +/- 4  meters     Pair B                 Normal
                                      Pair    B       0            +/- 4  meters     Pair A                 Normal
                                      Pair    C       1            +/- 4  meters     Pair C                Short
                                      Pair    D       2            +/- 4  meters     Pair D                Short
Test_Switch01#


Hope this will help you tell the facilities guys to check the cabling...




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