MST - Adding a new instance

[morabusa]

We have a customer with 400 Cisco switches running MST, and only making use of instance 0, which is the default instance where all VLANs are placed by default... I want to create two new instances, and move VLANs to the new instances, but I have the feeling that this could bring an outage. I am planning to start applying the configuration on the Root device, and then replicate it to other switches, but not sure if it is the best approach to do this. I have some questions:

1- Should I start applying the configuration on the Root switch (Core switch), or is it a better idea to start applying the confing on access switches?

2- What will happen when I create the new instances in the Root switch (Core switch), and then move some VLANs to the new instances, while this configuration is still not applied to other switches? Will this cause an outage, right? I am not sure about the behavior when we have MST configuration mismatch on some switches.

3- The customer is running VTP version 1 (I am not planning to change that for the moment), so it is not possible to replicate MST data base information between switches. Is there a way to replicate MST configuration aside from VTP (I think not)?

4- Any other advice you could give me is pretty much welcome.

Thanks.

[balaji.bandi]

VTP v1 scares me ( you need to move to VTPv2), adding MST with another instance will have convergence in the network.

good explained post here :

https://community.cisco.com/t5/switching/mst-adding-a-vlan-with-no-impact/td-p/1825297

[Flavio Miranda]

400 switches is a big infrasctructure. Why tis this  a flat network like that?  Why dont you break this topology?

Is this one build or more then one? I think you should start thinking Core>Distribution>Access and use Layer 3 in part of it.

There´s a high risk of loop on this topology.