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Err-disabled stat on cisco switch port

Posted on 2007-03-19
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Last Modified: 2008-04-05
I am intermittently having ports shut down on switches throughout my company. The switches I have are Cisco 3560 catalyst.  When I check the port it is in an err-disable state.  I can bring the port up by doing the shutdown no shutdown command on the interface.  When I check the status on the port to see why it went down the reason listed is bpduguard.  Bpduguard is enabled on the port. But my understanding was bpduguard detected bpdu packet.  I though bpdu packets only came from devices like switches.  The devices that are connected to the ports that go into the err-disable state are computers (Dell 9200).  Why would the switch think that the computers are sending out bpdu packets.
      
Any insight would be most appreciated.
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Question by:SHAX
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4 Comments
 
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Expert Comment

by:Don Johnston
ID: 18751997
SOMETHING caused a BPDU to come in that port. It could be that a user connected an unauthorized switch or maybe a cable got connected so that a loop was created.

The only time I've seen a computer generate a BPDU is if has multiple NIC's and it is configured to bridge the traffic between the NICs.

It sounds like some investigating is in order. :-o
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Author Comment

by:SHAX
ID: 20251522
*****Updated info for original post.*****  The NIC that we are seeing the BPDU's from are the Intel 82566 DC Integrated NIC in the Dimension 9200 desktop models.  As to the comment by donjohnson, the users are not plugging in unauthorized switches, nor have any cabling changes been made.  Thanks for the suggestion, but that isn't the case in this situation.  Any other comments and suggestions will be welcome.

Thanks
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by:Don Johnston
Don Johnston earned 500 total points
ID: 20253594
Do these PC's have wireless cards? If so, then the BPDU's could be arriving at the PC over the wireless link and the PC then passes it on to the switch.

The only way a PC will send out BPDUs:

1) There is more than on network interface on the PC and the PC is bridging the NICs.
2) The PC has a protocol analyzer and has previously captured BPDUs and is now sending them back out.
3) The PC is running a bridging service thereby making it a bridge.

It's got to be one of those.
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Accepted Solution

by:
SHAX earned 0 total points
ID: 20564904
Looks like the problem was a magic packet/wake on lan setting in the network card.  Once that was turned off I have not seen any more problems
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