Rookie question, cable test TDR

[bvj197222]

I did a cable test regarding an AP and got this output;

3560G#sh cable tdr interface gi0/13 
TDR test last run on: November 28 12:49:42

Interface Speed Local pair Pair length        Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi0/13    100M  Pair A     1    +/- 4  meters Pair B      Normal             
                Pair B     19   +/- 4  meters Pair A      Normal             
                Pair C     51   +/- 4  meters Pair C      Fail               
                Pair D     151  +/- 4  meters Pair D      Normal 

I've checked out this article, https://supportforums.cisco.com/document/74231/how-use-time-domain-reflectometer-tdr, and according to this the AP should not be getting any PoE. However, it's working fine. My question is how come the length for the different pairs are so much different? Pair A is 1 estimated one meter, and pair D is estimated 151 meters. This is one cable, shouldn't the length be approximately the same..?

[Leo Laohoo]

I'm the author of the article. 

The 3560G/E/X series has a "funny" way of doing TDR.  You are correct, the output you've posted should've mean that the AP shouldn't be getting PoE ... Unless you're looking at the wrong port (can you post the output to the command "sh power inline") or the AP is getting power from a power injector or power adapter.  

In regards to the "length" issue, this boils down to the hardware (of the switch), the "quality" of the cable and the IOS.  I have seen results like these on 3560 switches.  When I move the cables over to 3750G/E/X or 2960G/S the results were totally different.  Another thing to consider is the quality of the cable.  Really, really bad quality cable, regardless of switch model, will also contribute to a reading with different length values.

Another thing, what is the model of the AP and is this AP have a GigabitEthernet interface?  If the AP is capable of GigabitEthernet then it probably makes sense that the negotiated speed is only 100 Mbps instead of 1 Gbps.