Link up & down Repeatedly

[fbabashahi]

Hi , I have a switch 3750 stacked , I don't have IP-phone some of my links get up & down repeatedly (I see this in switches 2960 too)

Jul 1 10:24:12.159: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/3, changed state to down
Jul 1 10:25:03.831: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/3, changed state to up
Jul 1 10:25:04.838: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/3, changed state to up
Jul 1 10:25:07.815: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/3, changed state to down
Jul 1 10:25:08.814: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/3, changed state to down

The port config as below , I read that it might be for power inline so I disable it .

interface GigabitEthernet2/0/3
switchport mode access
power inline never
spanning-tree PORTFAST edge
spanning-tree BPDUGUARD enable

What should I do? 

How to prevent the port from this behavior?

[Leo Laohoo]

Post the complete output to the command "sh interface G2/0/3 controller". 

Then do the following: 

1.  Command:  test cable tdr interface G2/0/3

2.  Wait for approximately 5 to 7 seconds for the test to run it's course

3.  Command:  sh cable tdr interface G2/0/3

4.  Post the complete output to #3

[fbabashahi]

Hi @Leo Laohoo this is the output

SW-CORE# sh cable tdr interface G2/0/3
TDR test last run on: July 01 11:31:14

Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi2/0/3 auto Pair A 17 +/- 10 meters N/A Open
Pair B N/A N/A Normal
Pair C N/A N/A Normal
Pair D 17 +/- 10 meters N/A Short/Crosstalk

[Leo Laohoo]

---

@fbabashahi wrote:

Pair A 17 +/- 10 meters N/A Open
Pair B N/A              N/A Normal
Pair C N/A              N/A Normal
Pair D 17 +/- 10 meters N/A Short/Crosstalk

---

Faulty cable nearest the phone.  

[fbabashahi]

@Leo Laohoo

I don't understand i don't have phone in my network!!!

Also i did not change cabling. 

what does it mean? and what should i do?

[balaji.bandi]

Get new Patch cable ( cat 5/ Cat 6 - RJ 45)  and connect to end device and test it.

[Leo Laohoo]

The remote-end has a faulty cable.  

[MHM Cisco World]

BPDUguard make the interface err-disable and if you config the interface to be automatically UP again then you will face up down, 
just check when the interface is down 
show interface status,
check if interface is err-disable, 
I think the issue here is BPDUguard with interface connect to other L2 SW.