CCNA Switching and Network Access Practice Question
A network administrator is troubleshooting a switch port that is flapping between up and down states. The administrator suspects a duplex mismatch. Which command should be used to verify the duplex settings on the interface?
⚠ Common exam trap
The trap here is relying on 'show running-config' to see duplex, but that only shows configured values, not the operational values if auto-negotiation is in effect.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
show interfaces GigabitEthernet0/1
The 'show interfaces' command provides operational status, including duplex and speed, along with error counters that can indicate a duplex mismatch. It is the most reliable command to verify current duplex settings and diagnose related issues.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
show controllers GigabitEthernet0/1
Why it's wrong here
The 'show controllers' command provides low-level hardware statistics and is not typically used for duplex verification. It may show some physical layer information but is not the primary command for duplex settings and is less commonly used for this purpose.
- ✗
show running-config interface GigabitEthernet0/1
Why it's wrong here
This command shows the configured commands on the interface, including duplex settings if manually configured. However, it does not show the operational duplex if it is auto-negotiated. It is useful to see the intended configuration but not the actual current duplex.
- ✗
show interfaces status
Why it's wrong here
The 'show interfaces status' command provides a summary of interface status, including speed and duplex, but it may not show the configured duplex settings in detail. It is useful for a quick check but not as comprehensive as 'show interfaces' for troubleshooting duplex mismatches.
- ✓
show interfaces GigabitEthernet0/1
Why this is correct
The 'show interfaces' command displays detailed information about the interface, including duplex, speed, and error statistics. It will show if the duplex is set to full or half and can reveal mismatches. This is the most direct way to verify duplex settings.
Go deeper
Related to this question
Learn chapter
Network Topology Types
Key term
Switch
A switch is a networking device that connects devices on a local area network and uses MAC addresses to forward data only to the intended recipient.
Key term
Interface
An interface is a point of connection or interaction between two systems, devices, or software components that allows them to exchange information or signals.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.