200-301 Question #1333: Real Exam Question with Answer & Explanation

The correct answer is A: floods unknown destinations to all ports except the receiving port. When a switch receives a frame with an unknown destination MAC address, it floods the frame out all ports except the receiving port.

Submitted by ashley.k· Mar 5, 2026Network Fundamentals

Question

How does frame switching function on a switch?

Options

Afloods unknown destinations to all ports except the receiving port
Bmodifies frames that contain a known source VLAN
Crewrites the source and destination MAC address
Dbuffers and forwards frames with less than 5 CRCs

Explanation

When a switch receives a frame with an unknown destination MAC address, it floods the frame out all ports except the receiving port.

Common mistakes.

B. A Layer 2 switch primarily forwards frames based on destination MAC addresses and VLAN membership, not by modifying frames based on a known source VLAN.
C. Rewriting source and destination MAC addresses is a function of a router or devices performing Network Address Translation (NAT), not standard Layer 2 frame switching.
D. A switch checks for CRC errors to ensure frame integrity and drops corrupt frames, but the number of CRCs is not a forwarding criterion; frames with any CRC errors are typically discarded.

Concept tested. Layer 2 switching unknown unicast behavior

Reference. https://www.cisco.com/c/en/us/support/docs/lan-switching/ethernet-switches/10574-5.html

Topics

#Layer 2 switching#Frame forwarding#MAC address table#Unknown unicast flooding

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