Category Archives: PVST/PVST+

Layer 2 Traffic Engineering with Spanning Tree “cost” and “port-priority” Options

In this deep dive Spanning Tree supplemental techtorial we take an exhaustive look at the “spanning-tree cost” and “spanning-tree port-priority” commands and see why and how to implement them to perform Layer 2 traffic engineering. We start with an inductive approach by starting with the determining factors behind the Root Bridge election and then move on to the election of the Root Port (RP) on the non-Root Bridge and then what happens when there are multiple equal cost links to the Root Bridge. We then discuss the proper application of each command and go over how each command impacts the election of the Root Port (RP). Enjoy!