migration from rapid-pvst to mst

[Per_Cas]

Hello forum guys, 

I have three switches in LAN network which run in rapid-pvst mode. I would like migrate to mst.

I try to search cisco documentation and I found that migration from 802.1D to 802.1w is cousing outage:

http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/72844-MST.html

However I did not find any documents who could tell me about outage during migration from 802.1w to 802.1s. I would like to avoid any connectivity disruption if there is any during migration. How can I achieve this? As far as I know, mst has all features like rstp plus it can group set of vlans in defined instances, so theoretically, it should not be any connectivity disruption, should be? 

[Paul Chapman · Accepted solution]

Hi --

Any STP mode change will cause a 5-30 second disruption assuming you don't accidentally make an error.  The scope of the outage is based on where the STP root is and how many switches have to recalculate the tree.

PSC

[Per_Cas]

Hi Paul, 

Even change from rapid spt to mst ( so in fact from rstp to rstp ) ? 

[Paul Chapman]

You're proposing to change the protocol the switches use to negotiate.  Even if you configure multiple switches simultaneously, they still have to exchange the new type of BPDU and calculate the new topology.

PSC