[c-nsp] Tuning MST (MSTP)

[Alexandra Alvarado]

Hello,

The company where I work has a layer 2 networks, to have loop free, we have been configured
STP, but now STP is not enough because it only support 128 instance it means 128 vlans.
I need to configure more than 128 vlans, that's why I'm going to move to MST to group all
4094 vlans in 1 or 2 instance MST.

My questions:

1.- I read "By default, all VLANs are mapped to instance 0.". I want to divide my vlans in 2 
instance:

        instance 0 : Vlan 1-10
        instance 1: Vlan 11-4094

What is de advantage to manage all vlans in 1 instace?, or is better to divide the vlans in more 
the one instance.  

If I use 2 instance inspite 1 MST instance the broadcast wil reduce?

2.- Is the next config right or can I improve it and how?

Primary Root
-------------------
spanning-tree mode mst
spanning-tree loopguard default
spanning-tree portfast bpduguard default
no spanning-tree optimize bpdu transmission
spanning-tree extend system-id
!
spanning-tree mst configuration
 name region1
 revision 1
 instance 1 vlan 11-4094
!
spanning-tree mst 0-1 priority 24576

Secondary Root
-----------------------
spanning-tree mode mst
spanning-tree loopguard default
spanning-tree portfast bpduguard default
no spanning-tree optimize bpdu transmission
spanning-tree extend system-id
!
spanning-tree mst configuration
 name region1
 revision 1
 instance 1 vlan 11-4094
!
spanning-tree mst 0-1 priority 28672

Other switches
-----------------------
spanning-tree mode mst
spanning-tree loopguard default
spanning-tree portfast bpduguard default
no spanning-tree optimize bpdu transmission
spanning-tree extend system-id
!
spanning-tree mst configuration
 name region1
 revision 1
 instance 1 vlan 11-4094
!


Cost per Interfaces
---------------------------
spanning-tree mst 0-1 cost 1



Thanks

Alexandra Alvarado