STP Port States and Roles

Question 1

How many port states exist in the original IEEE 802.1D Spanning Tree Protocol?

Accepted Answer

5

Answer

IEEE 802.1D STP defines five port states: Blocking, Listening, Learning, Forwarding, and Disabled.

Question 2

In which STP port state does a switch port learn MAC addresses but NOT forward data frames?

Accepted Answer

Learning

Answer

In the Learning state, the port populates the MAC address table but still does not forward data frames to prevent loops.

Question 3

A port in the Blocking state will do which of the following?

Accepted Answer

Receive BPDUs but not forward data frames

Answer

A Blocking port listens to BPDUs to stay informed about the STP topology but discards all data frames to prevent loops.

Question 4

What is the default duration of the Listening state in IEEE 802.1D STP?

Accepted Answer

15 seconds

Answer

The Listening state lasts for one Forward Delay period, which defaults to 15 seconds in IEEE 802.1D.

Question 5

Which STP port state is functionally equivalent to the Discarding state introduced in RSTP (802.1w)?

Accepted Answer

Blocking

Answer

RSTP's Discarding state consolidates 802.1D's Blocking and Listening states, where the port neither learns MAC addresses nor forwards frames.

(STP) Spanning Tree Protocol Practice Test