Question

Difficulty: MediumSTP Port States and PortFast Benefits

An administrator issues the command `show spanning-tree interface gigabitethernet 0/1` on a Cisco Catalyst switch connected to a workstation. The command output indicates that the port is in the `FWD` state and lists `P2p Edge` under the Type column. Which operational behavior is directly associated with this interface status?

  1. The interface immediately transitions to the forwarding state upon linkup by bypassing the listening and learning states.Answer
  2. B
    The interface automatically filters all incoming Bridge Protocol Data Units (BPDUs) to prevent topology recalculation.
  3. C
    The interface can be safely configured on switch-to-switch trunk links to eliminate spanning-tree convergence timers.
  4. D
    The interface modifies the switch bridge priority by adding an incremental offset of 4096 to prevent root bridge election.

Answer

The interface immediately transitions to the forwarding state upon linkup by bypassing the listening and learning states.
When an interface is designated as an Edge port (PortFast enabled), it transitions directly to the forwarding state upon link activation. This bypasses the listening and learning states, preventing convergence delays for end-user workstations.

Step-by-Step Solution

1
Interpret the CLI output port type
The `P2p Edge` designation indicates that Cisco PortFast is enabled on a point-to-point link connected to an end device.
Edge ports in Spanning Tree Protocol represent host-facing connections that do not lead to another switch.
2
Identify the functional mechanism of PortFast
PortFast bypasses the 802.1D Listening (15s) and Learning (15s) states, placing the interface into Forwarding immediately upon link UP.
This allows hosts to quickly obtain IP address assignments via DHCP without timing out during boot.

Key Concept

PortFast / Edge Port State Transition and Convergence Mechanics
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