Change STP from RSTP to PVST+ , Will make switches down or any risk ?

[Ethan and Mia]

Hi master

I am looking the safety way for changing STP mode from  RSTP to PVST+

There 50 Switches running  If I change mode one by one. Any risk ? or any better way to do it.

Note * I had check no blocking state on any interface.

[balaji.bandi]

When you make the changes  the STP convergence take place, depends on your complex network and Layer2 domain streched,

So suggest to perform this maintenance window.

[Jitendra Kumar]

Such environments where you can't afford downtime never made such changes for the safe side and to avoid any miss-adventure. 

Always plan a Maintenance window and take a proper downtime

[MHM Cisco World]

it hard to answer this is L2 and L2 can not predictable. 
can I ask why change the STP ?

[Ethan and Mia]

Hello Thanks you for reply.

I need to change Rapid-STP to Per-VLAN-STP because I have 2 core net work switch 

example 

Switch-A = Root for VLAN100

Switch-B=Root for VLAN200

current stp is RSTP , Can't be separate  root of each VLAN right ?

I am not sure , can do like this on rapid-STP ?

thank i nadvance 

[MHM Cisco World]

Now I get this issue, you want to run PVST to make Load balance between two Core SW, 
the trunk is FWD for one VLAN and BLK for other VLAN. 
there are two rapid protocol RSTP can not do what you want, RPVST+ can do that 
show spanning tree summary give you which protocol you run 

[paul driver]

Hello
May I ask why you would change from RVST to the slower PVST

PVST doesn’t have the built-in features of rapid (backbone/uplinkfast) changing to PVST will mean so you will require to enable these manually if applicable.
I would suggest beginning at the edge layer and work your way upstream towards the core, this way the cores can continue to service any other non-migrated switch as RPVST until that switch is also migrated, then eventually migrate the cores

Lasty any stp migration will cause stp convergence so suggest to perform these changes out of hours under change windows.

[MHM Cisco World]

just want to mention it slower but excellent for load balance 

[Ethan and Mia]

Hello  Paul

Thank too much for reply

My case ... my network have many vlan but root of  vlan not on a switch. I would like to move to per vlan stp as well. or any recommend please advise. 

[Joseph W. Doherty]

Hmm, I recall (?) Cisco's rapid-STP is also a per VLAN variant.  So, believe you could have different roots (and preferred links) per VLAN.

If so, you really, as others have questioned, might want to keep to a your rapid-STP.

If you find your rapid-STP cannot support per-VLAN, then I would suggest migration to MST.

BTW, in answer to your question, moving a STP root will cause a brief outage (L2 topology needs to be recomputed).  Much longer for non-rapid-STP variants.

You can also intermix rapid-STP and non-rapid-STP, during a conversion.  Doing any conversion, will also cause outages, but possibly not impacting the whole L2 topology.

[Ethan and Mia]

Hello Thanks you for reply.

I need to change Rapid-STP to Per-VLAN-STP because I have 2 core net work switch 

example 

Switch-A = Root for VLAN100 (because server-VLAN100 on this switch)

Switch-B=Root for VLAN200  (because server-VLAN200 on this switch)

current stp is RSTP , Can't be separate  root of each VLAN right ?

I am not sure , can do like this on rapid-STP ?

thank in advance