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Cisco Catalyst 1900 Switches - dropping ports

Posted on 2002-03-25
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Last Modified: 2010-04-17
I have 3 Cisco switches, one of which is continually dropping ports.

Setup: Fibre links to switches 1 and 3, switch 2 has two redundant links ie 1 to 2 and 2 to 3.

Switch 2 occassionally drops ports. These ports are unable to ping anything.

I'm assuming that there is a configuration problem with the spanning tree algorithm resulting in ports to be foreced into a blocking state. However, I'm not sure how to troubleshoot this?

I have two vlans in use. As an initial step I removed spantree from both vlans, leaving it active only on vlan 1 (ie the management vlan). This seemed to settle the switch down, however port problems have once again become an issue. All cables and the switch itself have been swapped as well.

Does anyone have any suggestions?
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Question by:da_h
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by:lrmoore
ID: 6893989
try setting portfast on for all of your workstation ports, and keep spanning tree on all the uplink ports on all three switches...
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by:mikecr
ID: 6894543
I agree with Lrmoore. Normally when trunking switches you will use spanning tree on the trunked port. If you use it on all ports you sometimes have a problem.
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by:da_h
ID: 6896021
Thanks for the input guys

Unfortunately, I've already tried the above suggestions. I removed spantree from the two vlans used by machines on the network and left it active only on the management vlan. The management vlan is used by the trunking ports only.

Portfast was already enabled.

Any other suggestions? At this stage I'm thing a call to Cisco may be in order.


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by:mikecr
ID: 6896230
Are you using VTP to trunk your VLANS together?
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by:da_h
ID: 6896490
Yes, mikecr. Any ideas?
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by:mikecr
ID: 6897067
Without getting a lot of pages going here, check this article and make sure that you have your VTP set up according to Cisco. This will see if you may have overlooked something.
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by:mmedwid
ID: 6976388
Sounds to me like a duplex issue.  If the ports are set to AUTO detect - the workstations need to be set to auto.  And if the workstations were hard coded to FULL/100 - that would be a particular problem as the switches are only 10BT except for a couple of ports.  The ports would start generating lots of errors in a duplex mismatch and likely shut down.
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by:lrmoore
ID: 7997466
No comment has been added lately, so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area for this question:

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