2960s Link-Flap issue.

[robcoles001]

I've recently had a few ports on 48 way 2960s go in to err mode.

Bit of digging and they have been disabled due to link flapping. I disconnected the devices to check cables etc and all checked out. I've since repatched in another stacked 2960s without issue.

The switch with the issue seems to have got progressively worse, what started with a couple of ports now has gone to gi1/0/33-40 are now disabled due to flapping.Even though none of the ports are now in use. I've restarted the switch just in case it was having a special moment but no luck.

show log displays

000062: Dec 17 19:30:19.490: %PM-4-ERR_DISABLE: link-flap error detected on Gi1/0/40, putting Gi1/0/40 in err-disable state

Switch attempts to recover after 300s with no luck. Just to confirm there is nothing patched in to the effected ports.

Any suggestions or is it it RMA time.

[Leo Laohoo]

2960S supports a little well known featrue called TDR. 

Try this set of commands:

1.  Command:  test cable tdr interface ;

2.  Wait for about 5 to 7 seconds;

3.  Command:  sh cable tdr interface ; and

4.  Post the output to #3.

Make sure your switches are not running IOS version 15.0(2)SE.

[robcoles001]

Hello Leo Laohoo,

Thank you for the quick reply,

I mentioned earlier in the thread that I've unpatched and tested the cables and have moved the devices in to another switch all working fine. Ports also have recover on too, and still are in error mode.

Below is test result on one port which shows fine.

Interface Speed Local pair Pair length        Remote pair Pair status

--------- ----- ---------- ------------------ ----------- --------------------

Gi1/0/33  auto  Pair A     0    +/- 0  meters N/A         Normal

                Pair B     0    +/- 0  meters N/A         Normal

                Pair C     0    +/- 0  meters N/A         Normal

                Pair D     0    +/- 0  meters N/A         Normal

Regards

Rob

[robcoles001]

error recover is at 300s

[Leo Laohoo]

The TDR is not right.  In a large way.

The "Pair Status" shows it's Normal.  Which means it's OK, however, the distances to all four pairs is "0" plus the speed is "auto" or not detected. 

Run this command when the port is up/up. 

Also, when the port is Up/Up can you post the output to the command "sh interface Gi 1/0/33"?

[robcoles001]

there is nothing connected or patched in to that port.