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Difficulty: EasySTP Port States and PortFast Benefits

Which IEEE 802.1D Spanning Tree Protocol (STP) port state populates the switch MAC address table using source MAC addresses of received frames, but does not yet forward user data frames?

  1. LearningAnswer
  2. B
    Listening
  3. C
    Blocking
  4. D
    Forwarding

Answer

Learning
Under legacy 802.1D Spanning Tree Protocol, the Learning state acts as a transition phase between Listening and Forwarding. During this state, the switch port receives data frames and inspects source MAC addresses to populate its address table, but it continues to drop data traffic to maintain a loop-free environment.

Step-by-Step Solution

1
Analyze the operational requirements stated in the prompt.
The port state must populate the MAC address table based on incoming frame headers while continuing to discard user data frames.
Building the MAC address table before enabling full data transfer minimizes initial unicast flooding once data forwarding begins.
2
Evaluate the 802.1D STP port states against these requirements.
Blocking discards user data and does not learn MAC addresses. Listening evaluates network topology BPDUs without learning MAC addresses. Learning populates the MAC table but discards data frames. Forwarding both populates MAC tables and forwards data frames.
Only the Learning state satisfies the specific condition of MAC learning without data forwarding.

Key Concept

STP 802.1D Port States and Functions
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Topics

STP Port States and PortFast Benefits

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