- A
CRC errors
CRC errors indicate a mismatch in the frame check sequence, commonly due to physical layer issues like bad cabling or electromagnetic interference.
- B
Output queue drops
Why wrong: Output queue drops are typically caused by congestion and buffer exhaustion at Layer 3, not a Layer 1 issue.
- C
Runts
Runts are frames smaller than the minimum Ethernet size (64 bytes), often resulting from collisions or faulty hardware at Layer 1.
- D
Input errors
Why wrong: Input errors is a general counter that includes all receive errors, but it is not specific to Layer 1; it can include CRC, runts, giants, and framing errors.
- E
Ignored packets
Why wrong: Ignored packets are those dropped due to buffer overflow, often from high traffic or hardware limitations, not specifically a Layer 1 error.
CCNA Network Infrastructure and Connectivity Practice Question
This 200-301 practice question tests your understanding of network infrastructure and connectivity. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 interface error counters indicate a Layer 1 issue?
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
CRC errors
CRC errors occur when the cyclic redundancy check computed at the receiver does not match the value appended by the sender, indicating that the frame was corrupted during transmission. This corruption is typically caused by physical-layer problems such as faulty cabling, bad connectors, or excessive electrical noise. Runts are frames that are smaller than the minimum Ethernet frame size of 64 bytes (excluding preamble), and they often result from collisions or transceiver issues that are Layer 1 phenomena. Both counters directly point to physical-layer impairments rather than logical or congestion-related issues.
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
Why this is correct
CRC errors indicate a mismatch in the frame check sequence, commonly due to physical layer issues like bad cabling or electromagnetic interference.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Output queue drops
Why it's wrong here
Output queue drops are typically caused by congestion and buffer exhaustion at Layer 3, not a Layer 1 issue.
- ✓
Runts
Why this is correct
Runts are frames smaller than the minimum Ethernet size (64 bytes), often resulting from collisions or faulty hardware at Layer 1.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Input errors
Why it's wrong here
Input errors is a general counter that includes all receive errors, but it is not specific to Layer 1; it can include CRC, runts, giants, and framing errors.
- ✗
Ignored packets
Why it's wrong here
Ignored packets are those dropped due to buffer overflow, often from high traffic or hardware limitations, not specifically a Layer 1 error.
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.
✓CRC errorsCorrect answer▾
Why this is correct
CRC errors indicate a mismatch in the frame check sequence, commonly due to physical layer issues like bad cabling or electromagnetic interference.
✗Output queue dropsWrong answer — click to see why▾
Why this is wrong here
Output queue drops occur when the transmit queue is full due to congestion, typically at Layer 3 (IP) or Layer 2 (switching). They are not caused by physical layer issues but by traffic overload or insufficient buffer space.
Why candidates choose this
Students might confuse output drops with input errors, thinking any 'drop' could be physical, but output drops are purely a queuing mechanism issue.
✗Input errorsWrong answer — click to see why▾
Why this is wrong here
Input errors is a catch-all counter that includes CRC, runts, giants, and framing errors. While it can indicate Layer 1 issues, it is not specific to Layer 1 because it also includes errors from higher layers (e.g., alignment errors). The question asks for counters that indicate a Layer 1 issue, and input errors is too broad.
Why candidates choose this
Since input errors often include CRC and runts, students may think it directly indicates Layer 1, but it is a summary counter that can also include non-Layer1 errors.
✗Ignored packetsWrong answer — click to see why▾
Why this is wrong here
Ignored packets are dropped due to buffer overflow, often from high traffic or hardware limitations, not specifically a Layer 1 error. They are typically caused by congestion at Layer 2 or Layer 3, not physical layer faults.
Why candidates choose this
The term 'ignored' might suggest the interface is ignoring bad frames, but it actually refers to packets dropped because the receive buffer is full, which is a resource issue, not a physical layer error.
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 distinction between Layer 1 errors (CRC, runts, giants, frame errors) and Layer 2/3 congestion indicators (output drops, input drops, ignored counts), so the trap is that candidates mistakenly associate any 'drop' or 'error' counter with the physical layer without understanding the underlying cause.
Trap categories for this question
Command / output trap
Output queue drops are typically caused by congestion and buffer exhaustion at Layer 3, not a Layer 1 issue.
Detailed technical explanation
How to think about this question
CRC errors are detected by the Ethernet hardware using a 32-bit CRC field in the Ethernet trailer (IEEE 802.3). A single bit error anywhere in the frame (from destination MAC through payload) will cause the CRC to mismatch, and the frame is discarded. Runts can also be caused by a malfunctioning NIC that transmits partial frames or by a duplex mismatch where one side transmits before sensing the carrier, leading to collision fragments. In a real-world scenario, a long cable run with poor shielding might produce both CRC errors and runts simultaneously, while output queue drops would require a separate traffic-shaping analysis.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Network Infrastructure and Connectivity — study guide chapter
Learn the concepts, then practise the questions
- →
Network Infrastructure and Connectivity practice questions
Targeted practice on this topic area only
- →
All 200-301 questions
1,819 questions across all exam domains
- →
CCNA 200-301 v2 study guide
Full concept coverage aligned to exam objectives
- →
200-301 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 200-301 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Network Infrastructure and Connectivity practice questions
Practise 200-301 questions linked to Network Infrastructure and Connectivity.
Switching and Network Access practice questions
Practise 200-301 questions linked to Switching and Network Access.
IP Routing practice questions
Practise 200-301 questions linked to IP Routing.
Network Services and Security practice questions
Practise 200-301 questions linked to Network Services and Security.
AI and Network Operations practice questions
Practise 200-301 questions linked to AI and Network Operations.
CCNA subnetting practice questions
Practise IPv4 subnetting, CIDR, masks, host ranges and subnet selection.
CCNA OSPF practice questions
Practise OSPF neighbours, router IDs, metrics, areas and routing-table interpretation.
CCNA VLAN practice questions
Practise VLANs, access ports, trunks, allowed VLANs and switching scenarios.
CCNA STP practice questions
Practise spanning tree, root bridge election, port roles and STP troubleshooting.
CCNA EtherChannel practice questions
Practise LACP, PAgP, port-channel behaviour and bundle requirements.
CCNA ACL practice questions
Practise standard and extended ACLs, permit/deny logic and traffic filtering.
CCNA NAT practice questions
Practise static NAT, dynamic NAT, PAT and inside/outside address translation.
Practice this exam
Start a free 200-301 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
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: CRC errors — CRC errors occur when the cyclic redundancy check computed at the receiver does not match the value appended by the sender, indicating that the frame was corrupted during transmission. This corruption is typically caused by physical-layer problems such as faulty cabling, bad connectors, or excessive electrical noise. Runts are frames that are smaller than the minimum Ethernet frame size of 64 bytes (excluding preamble), and they often result from collisions or transceiver issues that are Layer 1 phenomena. Both counters directly point to physical-layer impairments rather than logical or congestion-related issues.
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 →
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.