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Difficulty: EasySwitching Concepts and VLANs

A switch receives an Ethernet frame on Port 1 with a destination MAC address that is currently not present in its MAC address table. Which action will the switch take to handle this frame?

  1. The switch floods the frame out all active ports within the same VLAN, except Port 1.Answer
  2. B
    The switch floods the frame out all active ports across all VLANs configured on the switch.
  3. C
    The switch forwards the frame directly to the default gateway router for Layer 3 resolution.
  4. D
    The switch drops the frame immediately unless it arrives on an 802.1Q trunk port with a matching native VLAN.

Answer

The switch floods the frame out all active ports within the same VLAN, except the receiving port.
When a switch receives a frame with a destination MAC address not listed in its MAC address table, it performs unknown unicast flooding. The frame is replicated and sent out every active port configured in the frame's VLAN, with the exception of the port on which the frame arrived.

Step-by-Step Solution

1
Examine the destination MAC address of the incoming Ethernet frame.
The destination address is identified as an unknown unicast address because it is missing from the switch MAC address table.
Switches query their Layer 2 forwarding table (CAM table) to match destination MAC addresses to specific egress ports.
2
Apply standard Layer 2 switch forwarding logic for unknown unicast traffic.
The switch floods the frame to all active interfaces assigned to the same VLAN, excluding the ingress port.
Flooding ensures the frame reaches the intended target host wherever it resides within that broadcast domain so the host can respond.

Key Concept

Unknown Unicast Flooding and Broadcast Domain Boundaries
Estimated Time:45s
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Topics

Switching Concepts and VLANs

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