Designing for Spanning Tree
To optimize data flow in the network, design and configure switches for the
following STP roles:
■ Primary and secondary root bridges (set priority values)
■ Designated and root ports (set port priorities/path cost)
■ Enable STP enhancements, such as Root Guard
Spanning Tree and PVST
With PVST (Per Vlan STP), there is a different instance of STP for each
VLAN. To derive the VLAN BID, the switch picks a different MAC address
from its base pool for each VLAN. Each VLAN has its own root bridge, root
port, and so on. You can configure these so that data flow is optimized, and
traffic load is balanced among the switches.
Spanning Tree is enabled by default on every VLAN.