Soru

Zorluk: KolayL2 Switching Concepts and MAC Table Operation

A Layer 2 switch receives an Ethernet frame with a unicast destination MAC address that does not currently exist in its MAC address table. Which two actions does the switch take upon receiving this frame?

  1. It floods the frame out all active interfaces in the VLAN except the ingress port.Cevap
  2. It examines the source MAC address of the frame and updates its MAC address table if the entry is missing.Cevap
  3. C
    It drops the frame immediately because the destination MAC address is unresolvable.
  4. D
    It forwards the frame to the default gateway router for MAC address resolution.
  5. E
    It sends a Layer 2 discovery protocol message to discover which port owns the destination MAC address.

Cevap

The switch populates its MAC address table using the ingress frame's source MAC address and floods the frame out all active switch ports within the VLAN, excluding the port on which the frame arrived.
When a Layer 2 switch receives a frame, it always inspects the source MAC address to learn or update its location in the MAC address table. If the destination MAC address is unknown, the switch performs an unknown unicast flood by forwarding the frame to all active interfaces in the VLAN, except the port on which the frame was received.

Adım Adım Çözüm

1
Inspect the incoming Ethernet frame header.
The switch identifies the frame's source MAC address and destination MAC address.
Learning and forwarding decisions are based on Layer 2 MAC addresses.
2
Process the source MAC address for learning.
The source MAC address is mapped to the ingress switch port in the MAC address table.
The MAC address table populates dynamically from incoming traffic source addresses.
3
Determine forwarding action based on destination MAC address lookup.
Since the destination MAC address is not found in the table, the frame is classified as unknown unicast and flooded out all ports except the receiving port.
Flooding ensures the frame reaches its intended destination even if its switch port location is currently unknown.

Anahtar Kavram

Switch learning mechanics and unknown unicast flooding
Bu soruyu puanla