err-disabled switch port

Unanswered Question
May 4th, 2009
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I have several ports on my network that I continue to see go into an err-disabled state when devices are connected to the network jack. I can fix these by doing a shut/no shut on the port, but I'm not sure what's causing this to happen?


No speed/duplex mismatches which has been the normal cause, so what else can cause this to happen? bad ethernet cables?


Thanks in advance.


/rls

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Giuseppe Larosa Mon, 05/04/2009 - 10:44
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Hello Robert,

if you have logging enabled examine the log there should be a message for this.


possible causes include:

port security

STP BPDUguard


and probably also port flapping (this can be caused by cabling)


5 up/down in 1 sec can trigger port flapping.


if the port just disabled is x/y


use

sh log | inc x/y




Hope to help

Giuseppe



rsamuel708 Mon, 05/04/2009 - 10:54
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I do see the port flapping error, but I'm not sure how that could be caused by cabling. Could you explain a little more?


Thanks.


/rls

Giuseppe Larosa Mon, 05/04/2009 - 11:29
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Hello Robert,

flapping is defined as frequent up/downs on the port for this I thought of a relationship with cabling issues (an intermittent link/wire in the RJ-45)


there is also an open issue about flapping on C2950 it is a bug.

We found it for frequent deregistration of VOIP phones caused by these up/downs

We tried last available IOS for C2950 but it didn't solve.


Hope to help

Giuseppe




rsamuel708 Mon, 05/04/2009 - 11:40
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Thanks Giuseppe, so you think the cables could have some physical problems that cause the port to flap, and then go into err-disable mode? All of the switches are newer 3750s.


/rls

Leo Laohoo Mon, 05/04/2009 - 16:07
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UDLS Port Aggressive can also cause a port to go into err-disable.

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