Spanning Tree Protocol (STP) convergence (Layer 2 convergence) happens when bridges and switches have transitioned to either the forwarding or blocking state. Normal Spanning Tree Protocol (STP) convergence (Layer 2 convergence) time is 50 seconds and the end user traffic is blocked until Root Port and/or Designated Port reach the forwarding state.
We can use the feature called Spanning Tree Protocol (STP) PortFast to speed up convergence on ports which are connected to a workstation, a network printer or a server (which are end devices and cannot cause layer 2 loops). PortFast feature should be used only to connect a single workstation to a switch port to avoid layer 2 switching loop. Spanning Tree PortFast feature causes a port to enter the forwarding state immediately, bypassing the listening and learning states.
When Spanning Tree Protocol (STP) is running, PortFast ports on the same switch can forward traffic between each other, but need to wait for Spanning Tree Convergence to communicate with a port on which the PortFast feature is disabled (normally a port connected to another switch).
Never enable PortFast on a Trunk port!