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Good day all,

We have some a mixed environment of Dell Powerconnect and Cisco switches. On both brands of switches, I am seeing numerous STP topology changes. I've decided to try on work on the Dell switches first. The root switch is a Cisco 6500.

Though the logs on the Dell switches show numerous topology changes within seconds, the root bridge remains the same. It is my understandings that topology changes should only really occur when switches are added or removed or root ports go down. Should I be concerned about these topology changes? Any help will be greatly appreciated. Thank you.

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up vote 2 down vote accepted

Are you actually seeing Toplogoy changes or are you seeing only Topology Change Notifications? If the latter than that's fairly normal but TCN's can cause a degree of network flooding if there are too many of them. One source of TCN's that can cause TCN flooding are host ports that aren't configured with the Cisco equivalent of portfast. If your host connected ports aren't configure for portfast they should be.

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Thanks for the feedback Joe! Now that you mention it, I do believe that it is TCNs rather than actual topology changes as the root switch remains the same Thanks for the advice on the Portfast. Dell's equivalent is Fast Link and it's not enabled, so I'm gonna enable that on the ports that connect to computers and see if that makes a difference. – Richard Apr 22 '13 at 17:49
Glad to help... – joeqwerty Apr 22 '13 at 17:52
Thus far I've enabled Fast Link on a Dell switch and the number the entries in the log regarding STP has stopped. Thank you! I'm going to try it on another Dell Switch and see how that responds. It is a bit of an administrative hassle though to go to each switch and enable the Fast Link on all the edge ports. Care will have to be taken when maintenance is being done on the switch and persons (edge ports) are moved. – Richard Apr 22 '13 at 19:24

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