C6509 Spanning tree rapid-pvst+

Unanswered Question
Jun 2nd, 2009


Working to change the STP mode on a production switch from PVST+ to rapid-pvst+

1-) What outage can I expect from production servers connected to this switch?

2-) What's the convergence time?

3-) Will be helpful to get a link where I educate myself on this topic.

Thanks a lot

I have this problem too.
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Giuseppe Larosa Tue, 06/02/2009 - 05:28

Hello Jeremie,

Rapid PVST is backward compatible with PVST on a per link basis: if the device sees version 1 in received BPDUs it detects neighbor is in PVST and reverts to PVST rule on this port.

When you change the STP mode on a device the following happens:

Rapid 802.1W STP instances one per vlan are created.

the legacy 802.1d STP instances are stopped

802.1W instances start to run.

the legacy 802.1d instances are removed.

For each instance the switch advertises itself and tries to discover the root bridge.

You need to consider at least 1 minute of out of service so you need a maintanance window.

The strategy can be that of moving to Rapid STP first one core switch, then on the access layer switches first and then at the end on the second core switch.



Hope to help



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