Error disabled problem in a switch

[tiwariharish44]

Hi,

We have a cisco 2960 switch that has its some ports getting error disabled time and again. When we issue show int fa0/X command, CRC and Input errors are seen.

The user has changed their LAN cable, we have replaced the LAN port at user end. But still the problem is there.

Now there is only one possibility that may be the cable running from switch to user LAN port is faulty. But can so many cables be faulty on the same switch??? Or can it be related to some IOS issue?

[InayathUlla Sharieff]

Hi

Error disabled due to what reason?

Did you change teh cable and port?

What is connected at the other end?

If the port is connected to LAN PC then have you changed the cable? If yes then is the lan driver updated? Is that same issue persits on all the ports of the switch or only one port?

HTH

[tiwariharish44]

Please see the output attached

The ports that are shown in the output go to error disable state time and again. And the reason is Link flap

Users connect laptop to these ports. Many users have used that port during last one year so this may not be a driver issue, I think. 

The LAN port as well as the LAN cable has been changed.

[InayathUlla Sharieff]

Okay its due to link flap.

Check the Layer 1.

[tiwariharish44]

what exactly to check in Layer 1 as we have checked everything except changing the cables running from switch to users' rooms. Thats the final thing we can do.

[InayathUlla Sharieff]

Explanation:- Link flap means that the interface continually goes up and down on a Cisco Switch. The interface will be put into the errdisabled state if it flaps more than five times in 10 seconds. The common cause of link flap is a Layer 1 issue such as a bad cable, duplex mismatch, or bad Gigabit Interface Converter (GBIC) card.

Below is the command to check the flap values:-

HTTS-C6K1#show errdisable flap-values

ErrDisable Reason    Flaps    Time (sec)

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

pagp-flap              3       30

dtp-flap               3       30

link-flap              5       10  >>>> Flap for 5 times.

The interface can be recovered from errdisable state by re-enabling the port using the errdisable recovery cause link-flap. This command is used to configure the recovery mechanism so that the interface can be brought out of the disabled state and allowed to try again. You can also set the time interval. Errdisable recovery is disabled by default in Cisco Switches; when enabled, the default time interval is 300 seconds.Once you enable the err disable state you can see the following log in the Cisco switch which is trying to recover the error disable interface (link-flap error)

Next Action:

=========

There are multiple things that could cause a link flap, usually the causes are hardware

layer issues like bad cable/ GBIC/FE port faulty, etc.

Have you tried replacing the cable and port both the ends?

What is connected at the other end and what kind of port is that?

[InayathUlla Sharieff]

Explanation:- Link flap means that the interface continually goes up and down on a Cisco Switch. The interface will be put into the errdisabled state if it flaps more than five times in 10 seconds. The common cause of link flap is a Layer 1 issue such as a bad cable, duplex mismatch, or bad Gigabit Interface Converter (GBIC) card.

Below is the command to check the flap values:-

HTTS-C6K1#show errdisable flap-values

ErrDisable Reason    Flaps    Time (sec)

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

pagp-flap              3       30

dtp-flap               3       30

link-flap              5       10  >>>> Flap for 5 times.

The interface can be recovered from errdisable state by re-enabling the port using the errdisable recovery cause link-flap. This command is used to configure the recovery mechanism so that the interface can be brought out of the disabled state and allowed to try again. You can also set the time interval. Errdisable recovery is disabled by default in Cisco Switches; when enabled, the default time interval is 300 seconds.Once you enable the err disable state you can see the following log in the Cisco switch which is trying to recover the error disable interface (link-flap error)

Next Action:

=========

There are multiple things that could cause a link flap, usually the causes are hardware

layer issues like bad cable/ GBIC/FE port faulty, etc.

Have you tried replacing the cable and port both the ends?

What is connected at the other end and what kind of port is that?

[tiwariharish44]

Thanks Inayathulla

We have changed the LAN port IO connector at user end. The cable from patch panel to the switch has also been changed.

And another point , in that switch , at least 4 ports LED is glowing amber despite having no cable connected to these ports. What could be the cause for that?

The IO LAN port at user end you can see in the attachement.

[Charles Hill]

Hello,

try 

show log | i err

this should return the ports that went in err-disabled mode and the reason.

Here is a link to a Cisco doc on causes of err-disabled ports.

http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/69980-errdisable-recovery.html#topic3

hope this helps.

if so, please rate.

thanks.

[paul driver]

Hello

show interface status err-disabled

Res

paul

[Charles Hill]

show interface status err-disabled is a much cleaner way of showing the reason for the error, versus the show log command.  However it only returns the reason while the port is currently disabled. 

After the port has been brought out of err-disabled state, you should be able to look in the log and see the reason.

[paul driver]

Hello

@cehill

if error recovery is enabled -as it seems it is in this case then sh int stat error-disabled will tell you the reason

you can also do:

show errdisable recovery

show errdisable detect

to see what error recovery features are enabled

res

paul

[Charles Hill]

Hey Paul,

Thanks for the info.  I seem to learn something new everyday looking over the postings.  I wish I would have participated more in the forums, years ago.  But, I guess its never too late.

Chuck

[tiwariharish44]

Please see the attachement . The reason is Link flap.

[Andre Neethling]

Firstly can you post the output of  "sh errdisable detect" please? Secondly can you confirm whether you are using "port security" or "BPDU guard"?