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Zorluk: OrtaSTP Port States and PortFast Benefits

An engineer executes the `show spanning-tree interface gigabitethernet 1/0/10` command on a Cisco switch after connecting a desktop PC. The output displays the port in the STP Learning state. What is the operational behavior of interface GigabitEthernet 1/0/10 while in this port state?

  1. The interface populates the MAC address table from incoming frames but does not forward user data traffic.Cevap
  2. B
    The interface actively forwards user data frames while preparing to send Topology Change Notifications.
  3. C
    The interface processes and transmits BPDUs but discards frame headers without updating the MAC address table.
  4. D
    The interface bypasses standard convergence timers because Cisco PortFast was enabled on the port.

Cevap

The interface populates the MAC address table from incoming frames but does not forward user data traffic.
In classic IEEE 802.1D Spanning Tree Protocol, the Learning state allows the switch port to learn source MAC addresses from frames received on the port and populate the switch MAC address table. However, to prevent Layer 2 loops while topology information stabilizes, the port does not yet forward user data frames or relay frames between interfaces.

Adım Adım Çözüm

1
Analyze standard 802.1D Spanning Tree Protocol port states in chronological sequence.
The progression order is Blocking → Listening → Learning → Forwarding.
Understanding the function of each state ensures correct identification of port behavior.
2
Examine the specific actions permitted during the Learning state.
The port receives and sends BPDUs, and reads incoming frames to populate the MAC address table, but user traffic forwarding remains disabled.
Learning MAC addresses before entering the Forwarding state reduces initial unicast flooding once forwarding begins.

Anahtar Kavram

802.1D STP Port State Operational Characteristics
Tahmini Süre:1m 15s
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STP Port States and PortFast Benefits

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