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CCNA Network Infrastructure and Connectivity Practice Question
Which of the following shows the correct order of steps to troubleshoot a suspected duplex mismatch and CRC errors on a Cisco IOS-XE interface?
⚠ Common exam trap
A common trap is to forget that you must enter global configuration mode before interface configuration mode. Another trap is to think that duplex and speed can be set globally, but they are interface-specific. Always remember the correct hierarchy: privileged EXEC -> global config -> interface config.
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
✓
Enter global configuration mode, then interface configuration mode for the affected interface, set duplex to full and speed to match the connected device, exit configuration mode, and verify the interface status.
The proper troubleshooting flow requires moving through the correct configuration hierarchy: from privileged EXEC mode you first enter global configuration mode. Then you specify the affected interface to enter interface configuration mode, where the duplex and speed settings are applied. After making the changes, you exit all configuration modes back to privileged EXEC and use show commands to verify the interface status. Option A follows this exact sequence. Option B is wrong because it tries to enter interface configuration without global config. Option C mistakenly attempts to set duplex/speed globally, which is not allowed. Option D not only omits global config but also exits to the wrong mode, leaving you in global configuration instead of privileged EXEC for verification.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Enter global configuration mode, then interface configuration mode for the affected interface, set duplex to full and speed to match the connected device, exit configuration mode, and verify the interface status.
Why this is correct
The correct sequence begins in privileged EXEC and enters global configuration mode with the configure terminal command. From there, interface configuration mode is entered using interface <type/number>, allowing the speed and duplex settings to be applied to the specific port that is experiencing the mismatch. After setting the two parameters, you exit to privileged EXEC where show interfaces or show interfaces status can verify that the link is up and the negotiated settings match the expected values.
- ✗
Enter interface configuration mode directly, set duplex and speed, then exit to privileged EXEC mode and verify the interface status.
Why it's wrong here
This answer fails because you cannot skip the global configuration mode plane; Cisco IOS requires entering configure terminal before you can enter interface configuration mode. Even if you could, the exit command from interface mode returns you to global configuration mode first, not directly to privileged EXEC, so the described verification method is also unrealistic. The correct path is configure terminal -> interface <type/number> -> set duplex/speed -> exit to privileged EXEC for show commands.
- ✗
Enter global configuration mode, set duplex and speed globally, then exit and verify the interface status.
Why it's wrong here
Duplex and speed are always configured per-interface in Cisco IOS; there is no global configuration command that sets these parameters across the entire device. Entering global configuration mode and attempting to apply these values would result in an invalid input error because the commands do not exist at that mode. Even if syntax were accepted, such a configuration would be meaningless, as different ports can require different speeds and duplex settings depending on the connected device.
- ✗
Enter interface configuration mode, set duplex and speed, then exit to global configuration mode and verify the interface status.
Why it's wrong here
This option reverses the required mode order: the CLI hierarchy demands global configuration mode first, so attempting to jump straight into interface configuration mode is invalid. Moreover, ending in global configuration mode does not give you access to the show commands needed to verify the interface status, which are available only in privileged EXEC mode. After configuring the interface, you must exit twice (interface -> global config -> privileged EXEC) to run the appropriate verification command.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Enter global configuration mode, then interface configuration mode for the affected interface, set duplex to full and speed to match the connected device, exit configuration mode, and verify the interface status.Correct answer▾
Why this is correct
The correct sequence begins in privileged EXEC and enters global configuration mode with the configure terminal command. From there, interface configuration mode is entered using interface <type/number>, allowing the speed and duplex settings to be applied to the specific port that is experiencing the mismatch. After setting the two parameters, you exit to privileged EXEC where show interfaces or show interfaces status can verify that the link is up and the negotiated settings match the expected values.
✗Enter interface configuration mode directly, set duplex and speed, then exit to privileged EXEC mode and verify the interface status.Wrong answer — click to see why▾
Why this is wrong here
This skips global configuration mode entirely. Interface configuration mode can only be reached after entering global configuration mode.
Why candidates choose this
Candidates might think they can jump directly to interface configuration mode from privileged EXEC mode, but the 'configure terminal' command is required first.
✗Enter global configuration mode, set duplex and speed globally, then exit and verify the interface status.Wrong answer — click to see why▾
Why this is wrong here
Duplex and speed are interface-specific commands; they cannot be applied at global configuration level.
Why candidates choose this
Candidates might confuse global configuration with interface-specific configuration, thinking that settings can be applied globally.
✗Enter interface configuration mode, set duplex and speed, then exit to global configuration mode and verify the interface status.Wrong answer — click to see why▾
Why this is wrong here
This sequence incorrectly assumes one can enter interface configuration directly and also exits back to global configuration mode instead of to privileged EXEC for verification.
Why candidates choose this
Candidates might think they can go directly to interface config and then exit to global config, but the correct flow is global -> interface -> exit (to privileged EXEC) -> verify.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Go deeper
Related to this question
Learn chapter
Half-Duplex vs Full-Duplex
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.
Key term
Cyclic Redundancy Check
A Cyclic Redundancy Check (CRC) is an error-detecting code used to verify that data transmitted over a network or stored on a device has not been corrupted.
About these practice questions
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.