When is the Root Bridge placement form of STP load balancing most effective? What command(s) are used to implement this approach?
When traffic patterns are well defined and clearly understood. In hierarchical networks such as those adhering to the multilayer design model discussed in Chapters 14 and 15, Root Bridge placement is an extremely effective form of STP load balancing. Simply collocate the Root Bridge with the corresponding default gateway router for that VLAN (see Chapters 14 and 15 for information). For non-hierarchical, flat-earth networks, load balancing usually requires different VLANs to have server farms in different physical locations.
When placing Root Bridges, either the set spantree priority or the set spantree root commands can be used.