- A
CRC errors are always caused by a faulty switch port and require port replacement.
Why wrong: CRC errors are usually caused by cabling issues or electromagnetic interference, not necessarily a faulty port.
- B
A high number of runts on an interface typically indicates excessive collisions or a faulty NIC.
Runts are frames smaller than 64 bytes and often result from collisions (e.g., in half-duplex) or a malfunctioning NIC that generates undersized frames.
- C
Giants are frames that exceed the maximum transmission unit (MTU) and are always discarded by the switch.
Why wrong: Giants are frames larger than the maximum allowed size, but some switches may forward them if configured for jumbo frames; they are not always discarded.
- D
Output errors, including late collisions, can be caused by a duplex mismatch between the switch and the connected device.
A duplex mismatch (e.g., one side full-duplex, the other half-duplex) leads to late collisions and other output errors due to timing issues.
- E
The 'show controllers' command provides a detailed view of CRC errors but does not show runts or giants.
Why wrong: 'show controllers' displays hardware-level details including CRC errors, but it can also show runts, giants, and other frame errors depending on the platform.
Quick Answer
The answer is that CRC errors often stem from faulty cabling or interference, while runts—frames smaller than 64 bytes—are typically caused by collisions on half-duplex links or a faulty NIC. CRC errors indicate a data integrity failure at the frame check sequence level, meaning the frame arrived with corrupted bits, which is rarely a switch port defect but almost always a physical-layer issue like bad wiring or electromagnetic interference. Runts, by contrast, are truncated frames resulting from collisions, where a frame is cut short before reaching the minimum size, or from a malfunctioning network interface card. On the CCNA 200-301 v2 exam, this distinction tests your ability to read 'show interface' output and isolate layer 1 versus layer 2 problems—a common trap is blaming the switch port for CRC errors when the cable is the culprit. Remember the mnemonic: CRC = Cable, Runts = Collisions.
CCNA Network Infrastructure and Connectivity Practice Question
This 200-301 practice question tests your understanding of network infrastructure and connectivity. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which TWO statements correctly describe the causes or implications of CRC errors, runts, giants, or output errors as seen in the output of 'show interface' or 'show interface status'?
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
A high number of runts on an interface typically indicates excessive collisions or a faulty NIC.
Option B is correct because runts—frames smaller than 64 bytes—often result from collisions truncating frames on half-duplex links or a faulty NIC. Option D is correct because duplex mismatch can cause late collisions, which appear as output errors in 'show interface'; a device on one side full-duplex and the other half-duplex leads to collisions and framing errors. Option A is wrong because CRC errors can stem from faulty cabling, interference, or a mismatched NIC, not exclusively a bad switch port. Option C is wrong because giants (frames over maximum MTU) may be forwarded if the interface is configured with jumbo frames or the switch is set to accept oversize frames. Option E is wrong because 'show controllers' displays frame-size errors like runts and giants, including details beyond CRC errors.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
CRC errors are always caused by a faulty switch port and require port replacement.
Why it's wrong here
CRC errors are usually caused by cabling issues or electromagnetic interference, not necessarily a faulty port.
- ✓
A high number of runts on an interface typically indicates excessive collisions or a faulty NIC.
Why this is correct
Runts are frames smaller than 64 bytes and often result from collisions (e.g., in half-duplex) or a malfunctioning NIC that generates undersized frames.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Giants are frames that exceed the maximum transmission unit (MTU) and are always discarded by the switch.
Why it's wrong here
Giants are frames larger than the maximum allowed size, but some switches may forward them if configured for jumbo frames; they are not always discarded.
- ✓
Output errors, including late collisions, can be caused by a duplex mismatch between the switch and the connected device.
Why this is correct
A duplex mismatch (e.g., one side full-duplex, the other half-duplex) leads to late collisions and other output errors due to timing issues.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The 'show controllers' command provides a detailed view of CRC errors but does not show runts or giants.
Why it's wrong here
'show controllers' displays hardware-level details including CRC errors, but it can also show runts, giants, and other frame errors depending on the platform.
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.
✓A high number of runts on an interface typically indicates excessive collisions or a faulty NIC.Correct answer▾
Why this is correct
Runts are frames smaller than 64 bytes and often result from collisions (e.g., in half-duplex) or a malfunctioning NIC that generates undersized frames.
✗CRC errors are always caused by a faulty switch port and require port replacement.Wrong answer — click to see why▾
Why this is wrong here
This statement is too absolute; CRC errors often stem from Layer 1 issues like bad cables or noise, not always a defective port.
✗Giants are frames that exceed the maximum transmission unit (MTU) and are always discarded by the switch.Wrong answer — click to see why▾
Why this is wrong here
The statement is too definitive; giants can be forwarded if jumbo frame support is enabled.
✗The 'show controllers' command provides a detailed view of CRC errors but does not show runts or giants.Wrong answer — click to see why▾
Why this is wrong here
This statement is incorrect because 'show controllers' often includes runt and giant counters on many Cisco platforms.
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?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that CRC errors always indicate a bad port (trap A) and that giants are always discarded (trap C), when in reality both can have multiple causes and switches can be configured to forward larger frames.
Trap categories for this question
Command / output trap
'show controllers' displays hardware-level details including CRC errors, but it can also show runts, giants, and other frame errors depending on the platform.
Detailed technical explanation
How to think about this question
CRC errors indicate a frame-level checksum mismatch, often due to physical-layer issues like bad cabling or signal degradation, and are counted on the receiving interface. Runts below 64 bytes are typically fragments from collisions in half-duplex environments, but in full-duplex links they almost always point to a hardware fault. Output errors like late collisions occur when a frame is transmitted after the collision window (512 bit-times) has passed, which is a classic symptom of a duplex mismatch where one side is half-duplex and the other full-duplex.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 200-301 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 200-301 question test?
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A high number of runts on an interface typically indicates excessive collisions or a faulty NIC. — Option B is correct because runts—frames smaller than 64 bytes—often result from collisions truncating frames on half-duplex links or a faulty NIC. Option D is correct because duplex mismatch can cause late collisions, which appear as output errors in 'show interface'; a device on one side full-duplex and the other half-duplex leads to collisions and framing errors. Option A is wrong because CRC errors can stem from faulty cabling, interference, or a mismatched NIC, not exclusively a bad switch port. Option C is wrong because giants (frames over maximum MTU) may be forwarded if the interface is configured with jumbo frames or the switch is set to accept oversize frames. Option E is wrong because 'show controllers' displays frame-size errors like runts and giants, including details beyond CRC errors.
What should I do if I get this 200-301 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jun 11, 2026
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.
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