Question 1hardmultiple choice
Full question →- → Why each wrong option is wrong in this specific scenario
- → When each wrong option would be correct
- → Real-world analogy and exam trap analysis
- → Related glossary terms and similar practice questions
Question 1,107 of 1,052
hardmultiple choiceObjective-mapped
CCNA Practice Question: Notices that users on VLAN 100 are experiencing…
This 200-301 practice question tests your understanding of 200-301 exam topics. 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.
Exhibit
Switch#show interfaces GigabitEthernet0/1
GigabitEthernet0/1 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is 001a.6c3e.7b01 (bia 001a.6c3e.7b01)
Description: AP_VLAN100
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/s, media type is 10/100/1000BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:01, output 00:00:01, output hang never
Last clearing of "show interface" counters 00:05:00
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
12345 packets input, 1234567 bytes, 0 no buffer
Received 10000 broadcasts (0 multicast)
0 runts, 0 giants, 0 throttles
150 input errors, 0 CRC, 0 frame, 150 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
0 input packets with dribble condition detected
12345 packets output, 1234567 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out
Switch#show interfaces status
Port Name Status Vlan Duplex Speed Type
Gi0/1 AP_VLAN100 connected 100 a-full a-1000 10/100/1000BaseTX
Gi0/2 notconnect 1 auto auto 10/100/1000BaseTX
Gi0/3 connected 1 a-full a-1000 10/100/1000BaseTX
Gi0/4 connected 1 a-full a-1000 10/100/1000BaseTXA network engineer notices that users on VLAN 100 are experiencing intermittent connectivity. The switch port connected to the access point for VLAN 100 shows frequent link flaps and input errors. Based on the output of 'show interfaces GigabitEthernet0/1' and 'show interfaces status', what is the most likely cause of the issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
✓
Faulty Ethernet cable causing excessive overrun errors
The interface shows 150 input errors, all overruns, with no CRC or frame errors, and the link is up at 1000 Mb/s full duplex. Overrun errors indicate the input rate exceeds the hardware buffer capacity, often due to a speed mismatch or faulty cable. However, the speed is negotiated as 1000 Mb/s, and the issue is likely a hardware fault on the cable or NIC causing excessive buffering. The flaps (not shown in counters but implied by intermittent connectivity) and overruns point to a cable fault rather than duplex mismatch (which would show late collisions) or speed mismatch (which would cause CRC errors).
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Duplex mismatch between the switch and the access point
Why it's wrong here
Duplex mismatch would typically cause late collisions and CRC errors, not overruns. The interface shows full duplex on both sides, so this is not the issue.
- ✓
Faulty Ethernet cable causing excessive overrun errors
Why this is correct
Overrun errors indicate the switch's input buffer is overwhelmed, often due to a faulty cable causing retransmissions or noise, leading to intermittent connectivity. The lack of CRC errors suggests the issue is not alignment but buffer exhaustion.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
- ✗
Speed mismatch between the switch and the access point
Why it's wrong here
The 'show interfaces status' shows speed as a-1000 (auto-negotiated 1000 Mb/s), so both sides agree on speed. Speed mismatch would cause CRC errors or link down, not overruns.
- ✗
Broadcast storm on VLAN 100
Why it's wrong here
A broadcast storm would show high input rates and broadcasts, but the input rate is 0 bits/sec, and only 10000 broadcasts were received in 5 minutes. Overruns are not typical of broadcast storms.
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.
✓Faulty Ethernet cable causing excessive overrun errorsCorrect answer▾
Why this is correct
Overrun errors indicate the switch's input buffer is overwhelmed, often due to a faulty cable causing retransmissions or noise, leading to intermittent connectivity. The lack of CRC errors suggests the issue is not alignment but buffer exhaustion.
✗Duplex mismatch between the switch and the access pointWrong answer — click to see why▾
Why this is wrong here
No late collisions or CRC errors are present; both sides are full duplex.
✗Speed mismatch between the switch and the access pointWrong answer — click to see why▾
Why this is wrong here
Speed is auto-negotiated and matches; no CRC errors are present.
✗Broadcast storm on VLAN 100Wrong answer — click to see why▾
Why this is wrong here
Input rate is low, and no broadcast storm symptoms like high CPU or packet drops are evident.
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: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Trap categories for this question
Command / output trap
Duplex mismatch would typically cause late collisions and CRC errors, not overruns. The interface shows full duplex on both sides, so this is not the issue.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
- Access ports place end devices into a single VLAN.
- Trunk ports carry multiple VLANs between switches.
- Allowed VLAN lists decide which VLANs can cross a trunk.
- Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
- Use show vlan brief to verify access VLANs.
- Use show interfaces trunk to verify trunk state and allowed VLANs.
- Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Got this wrong? Here's your next step.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
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.
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.
CCNA DHCP practice questions
Practise DHCP scopes, relay, leases and troubleshooting.
CCNA show ip route practice questions
Practise routing-table output, longest-prefix match, AD and route selection.
CCNA show interfaces trunk practice questions
Practise trunk verification and VLAN forwarding across switches.
CCNA wireless security practice questions
Practise WLAN security, authentication and wireless architecture concepts.
CCNA IPv6 practice questions
Practise IPv6 addressing, routes, neighbour discovery and common IPv6 exam traps.
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?
Access ports place end devices into a single VLAN.
What is the correct answer to this question?
The correct answer is: Faulty Ethernet cable causing excessive overrun errors — The interface shows 150 input errors, all overruns, with no CRC or frame errors, and the link is up at 1000 Mb/s full duplex. Overrun errors indicate the input rate exceeds the hardware buffer capacity, often due to a speed mismatch or faulty cable. However, the speed is negotiated as 1000 Mb/s, and the issue is likely a hardware fault on the cable or NIC causing excessive buffering. The flaps (not shown in counters but implied by intermittent connectivity) and overruns point to a cable fault rather than duplex mismatch (which would show late collisions) or speed mismatch (which would cause CRC errors).
What should I do if I get this 200-301 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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 →
Keep practising
More 200-301 practice questions
- A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that w…
- A switch has DHCP snooping enabled, but users still experience IP-to-MAC spoofing attacks. Which additional feature shou…
- Switch SW1 sends traffic for VLAN 30 across a trunk to SW2, but hosts in VLAN 30 on SW2 cannot communicate with hosts in…
- What problem is HSRP designed to solve?
- Which DHCP message does the client send to formally accept an offered address?
- What metric does RIP use to choose the best path?
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.
Loading comments…
Sign in to join the discussion.
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.