When a switch boots it participates in the STP convergence process to determine which of its ports will root or designated ports, and which ports must block the flow of traffic. During the convergence process each switch port goes through four STP states, in the order presented in the. Most students are familiar with the basics of (classic) spanning tree: how a root bridge is elected, how the switches decide what interfaces become designated, non-designated, root ports, etc. Once the topology has converged, it doesn't stop. Also there are other changes like the addition of switch or failure of port of an existing switch. The switches elect a single switch as the root bridge. HTH It's essentially the process of a dynamic routing protocol noticing “oh no one. Some people state that convergence follows this schematics: Others state that each port cycles through 4 states (Blocking, Listening, Learning, Forwarding). For me, both "models".
[PDF Version]