Errordisable recovery test

Unanswered Question
Feb 11th, 2010
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We are trying to test err disable recovery on Cisco 2960 switches. Here is what we have connected:

Cisco 2960-24TC-S --> Cisco 2960-24LT-L --> Asante 8 port (dumb hub) --> pc

We have done to following to make the port on the Cisco 2960-LT-L fail (err-disable mode):

Using crossover cables loop ports 1/2 and 3/4

From PC (port 5) ping broadcast address -

The dumb hub is connectd to the Cisco 2960-24LT-L (port 2).  It does not fail.  Shouldn't it fail with all of the loops from the dumb hub?

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jfraasch Thu, 02/11/2010 - 11:59
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I am guessing you are trying to invent your own STP loop to force an errdisable condition on the Cisco.

The best way to do that is to simply plug two your hub ports into differnt ports on the Cisco device.

STP finds a loop by looking at the BPDUs of the downstream device.  If it sees BPDUs coming from the same device across two cables, it should errdisable one of the ports.

Your PC can be connected to the hub still and you should still be alright to ping.

Hope that helps.


Leo Laohoo Thu, 02/11/2010 - 13:34
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Try this ...
Enable spanning-tree portfast and spanning-tree BPDUguard and connect a network cable into one port and the other end to another port of the same switch.


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