12.2(58)SE2, 3750X and PoE problem

[Jose_Miguel5673]

Hi,

we are running some 3750x´s switches as an access device for VoIP phones and PC´s. Lately we are having some issues conecting IP phones as we can see that the port links up (we can see the led blinking) but if we issue the "show ip int brief" to check the ports we can see the iin Down state.

Port1=>IP Phone1+PC1: Does not work

Port2=>IP Phone2+PC2: Works fine

Port1=>PC1: Works fine

Port1=>IP Phone1: Does not work

Port2=>IP Phone1+PC2: Works fine

Port1=>IP Phone2+PC1: Does not work

We guess it is a faulty port but it is a bit strange that it had hapens on some ports. Could it be as simple as a faulty port or there is something behind the scenes...

[Leo Laohoo]

Do this:

1.  Command:  test cable tdr interface ;

2.  Wait for 5 to 7 seconds;

3.  Command:  sh cable tdr interface ; and

4.  Post the output to #3.

[Mercedes Hernan]

sho cable-diagnostics tdr interface gigabitEthernet 2/0/17
TDR test last run on: November 27 13:39:37

Interface Speed Local pair Pair length        Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi2/0/17  auto  Pair A     1    +/- 10 meters N/A         Open               
                Pair B     8    +/- 10 meters N/A         Open               
                Pair C     8    +/- 10 meters N/A         Open               
                Pair D     9    +/- 10 meters N/A         Open     

[Leo Laohoo · Accepted solution]

Open circuit?  There's nothing connected at the remote end. 

However, your patch cable nearest the switch could be faulty.  Look the the "lengths".  Pairs B, C and D are showing 8 to 9 metres but Pair A is showing only 1. 

[Jose_Miguel5673]

Hi Leo,

as you guessed pretty well, there was nothing connected but the command you showed us was very helpful cause we could determine that where wire was faulty.

Also we could see that it happends on several customer worktable.

Thank you very much dude!!!

[Leo Laohoo]

Thanks for taking the time to rate our posts, Jose. 

Please be cautious about the IOS version you are using because it is very buggy. 

Use either 12.2(55)SE8 or 15.0(2)SE4.

[Jose_Miguel5673]

What else... You helped me and I helped you.

I have read a lot about the bugs the version has but, so far, no problem has been detected on our CPU loads.

Again, thank you very much for helping us.

[Leo Laohoo]

Want to know more about the commands above?  Read this:  How to use Time-Domain Reflectometer (TDR)