This cfg is based on the MST domain 
becoming the CIST root for the whole estate

All mst instances having their priority's lower
than any pvst switch





			
			site A
			------
C9K-1
stp mst
all instances (inc 0) priority 16384

6509
stp pvst
vlan 1 priority = 61440
All other vlans = priority 57344



C9k-2
stp pvst
All vlans = priority 61440




			site B
			------
C9K-1 <cist root>
stp mst
all instances (inc 0) priority 0

apply guard root on links interconnecting site A-C



C9K-2 (spoke)
stp pvst
vlan 1 priority = 61440
All other vlans = priority 57344




			
			site C
			------
M3600
stp pvst
vlan 1 priority = 61440
All other vlans = priority 57344

any switch behind M33600 set All vlans = priority 61440