how can i change MST to rpvst in production environment without problems

[aitdrift1]

We are planning to change MST to rpvst in our network that is cisco based.

What should i take care of while changing the stp mode from MST to rpvst.

[InayathUlla Sharieff]

A switch running both MSTP and RSTP supports a built-in protocol 
migration process that enables the switch to interoperate with legacy 
802.1D switches. If this switch receives a legacy 802.1D configuration 
BPDU (a BPDU with the protocol version set to 0), it sends only 802.1D 
BPDUs on that port. An MSTP switch can also detect that a port is at the 
boundary of a region when it receives a legacy BPDU, or an MST BPDU 
(version 3) associated with a different region, or an RST BPDU (version 
2). 

However, the switch does not automatically revert to the MSTP mode if it 
no longer receives 802.1D BPDUs because it cannot determine whether the 
legacy switch has been removed from the link unless the legacy switch is 
the designated switch. A switch also might continue to assign a boundary 
role to a port when the switch to which it is connected has joined the 
region. 

To restart the protocol migration process (force the renegotiation with 
neighboring switches) on the entire switch, you can use the clear 
spanning-tree detected-protocols privileged EXEC command. To restart the 
protocol migration process on a specific interface, enter the clear 
spanning-tree detected-protocols interface interface-id privileged EXEC 
command. 

[InayathUlla Sharieff · Accepted solution]

 We don't have a document on converting from MST
to another protocol but the procedure is the same if you were going to
MST. 

http://www.cisco.com/en/US/products/hw/switches/ps708/products_configura
tion_example09186a00807b075f.shtml#mst1

Because MST uses RSTP for timers, they are compatible with each other.
The only thing you have to ensure when converting back is that make sure
you have the lowerst priority for all vlans set correctly on the VSS so
VSS is the root bridge for all vlans. There will be a convergence when
to change protocols but it will be minimal as RSTP has faster
convergence timers. 

HTH

Inayath

[aitdrift1]

Thanks a lot for the answer, I was wondering one thing, we want to keep our root switch the same, so is it best to begin changing the stp mode on distribution switches first and then the core  switch and in the last changing the root switch. 

Because if we change the root switch first to become the root then the whole network will start recalculating paths, but if we change distribution switches first then only that switch will recalculate first and only those servers will be affected.

And also before starting that should i change vlan priorities on the root switch to maintain the root status.

[InayathUlla Sharieff]

Yes but its really up to you sit have paper diagram in front of you..plan from were you want to start and go untill you finish.

Make sure you do all the changes in the MW .

HTH

[aitdrift1]

We started to change the stp protocol from access layer switches towards the core by keeping our root switch in mst domain all the time and everything went smoothly and in the end we changed the stp mode on the root switch and made it primary root for all vlans it went perfekt for us. Thanks for the help.
 

[InayathUlla Sharieff]

thanks for the update. Happy to hear the news.