err-disabled switch port

[rsamuel708]

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

[Giuseppe Larosa]

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]

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]

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]

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]

UDLS Port Aggressive can also cause a port to go into err-disable.

[Eric Kenny]

You can set the switch to automatically recover from an error disabled state, that way you don't have to waste your time logging in to the switch and shut/noshutting the port.

See here: http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00806cd87b.shtml#topicsub1