Spanning Tree Topology Change Notification (TCN)

Lessons Discussion
123

Thank you David for the confirmation.

124

Hello Fritz

@davidilles is indeed correct, it is enabled by default on Cisco switches. However, itā€™s important to understand that TCN is not a separate feature you can toggle on or off. Rather, it is an integral, fundamental mechanism of STP itself. Since STP is enabled by default on Cisco Catalyst switches, the TCN mechanism is automatically active.

So you canā€™t ā€œdisableā€ TCNs on an STP implementation. You can, however, control how they are generated and responded to. This is done using PortFast, which disables TCN generation on edge ports, or you can use RSTP, which doesnā€™t use separate TCN BPDUs, but integrates the TCN mechanism in its generic BPDUs.

I hope this has been helpful!

Laz

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125

Hi Lazarus, this is helpful. Thank you so much.

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