Here is a scenario with switches running STP and exchanging information as
shown above. From this information, exchange will yield the following final
results:
- The election of a root bridge as a Layer 2 topology point of reference
- The determination of the best lowest cost path to the root bridge
- The election of a designated switch and corresponding designated port for
every switched segment
- The removal of loops in the switched network by transitioning redundant
switch ports to a disabled port role
- Determination of the "active topology" for each instance or VLAN
running STP
The active topology is the final set of communication paths that are
created by switch ports forwarding frames. Once the active topology has been
established, using Topology Change Notifications, the switched network must
reconfigure the activity topology if a link failure occurs.