Strange behavior on CE500 when port changes to forwarding

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Oct 2nd, 2008
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The attachment illustrates a example network topology that can be used to demonstrate an issue that we have noticed with the CE500 switch. In this example PC1 and PC2 are exchanging data using a proprietary protocol riding on 802.3. PC3 is just monitoring network traffic, which consists of spanning tree packets and a intermittent broadcast that is sent out by PC1. All ports are set to Smartport Role=Other.

A loop is added between 2 ports. In this example there is no reason to have a loop here, but in our real network this loop represents a chain of devices with a redundant path for data in the event of a link failure. Immediately after this loop is formed both port lights are Orange while the spanning tree state is figured out. Eventually, one of these ports transitions from orange to green (spanning tree state Learning->Forwarding). It is at this moment that the network exhibits strange behavior lasting for approximately 1 second.

It appears that during this time the mac address table of the switch is getting cleared (or ignored). The traffic that would normally exist between PC1 and PC2 can be seen at PC3. An even more interesting observation is that sometimes packets sent from PC2 to PC1 end up back a PC2 during this time.

We have tried other brands of switches and do not see this specific behavior.

Any ideas about what might be going on here?

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jasondaughenbaugh Tue, 10/07/2008 - 08:20
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I'm replying to my own post in an attempt to bring this thread back to life. Does anyone have any ideas/thoughts on this issue that I am seeing?



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