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Question 767 of 1,052
hardmultiple choiceObjective-mapped
CCNA Practice Question: A network technician is troubleshooting…
This 200-301 practice question tests your understanding of a network technician is troubleshooting…. 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
SwitchA# show interfaces GigabitEthernet0/1
GigabitEthernet0/1 is up, line protocol is down
Hardware is Gigabit Ethernet, address is aabb.cc00.0101 (bia aabb.cc00.0101)
Description: Link to SwitchB Gi0/1
Internet address is 192.168.10.1/24
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 never, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (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
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
0 input packets with dribble condition detected
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 1 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 outA network technician is troubleshooting connectivity between two directly connected Cisco switches. Hosts on VLAN 10 connected to SwitchA cannot ping the default gateway on SwitchB. The interface on SwitchB shows up/up, but the interface on SwitchA shows up/down. The technician examines the interface configuration and status on SwitchA. What is the most likely cause of this 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
✓
Configure both interfaces with the same duplex and speed settings, either both auto or both manually set to full-duplex and 1000 Mbps.
The interface on SwitchA is up but the line protocol is down, indicating a Layer 1 (physical) issue but Layer 2 is not operational. The key clue is that the interface is set to full-duplex and 1000Mb/s, but there are no errors. However, the problem is that the interface speed is manually configured to 1000 Mbps, but the cable or the remote switch may not support gigabit speeds, or the remote interface is configured differently. In this scenario, the most common cause is a duplex mismatch: if SwitchB's interface is set to auto-negotiate and defaults to half-duplex due to a negotiation failure, the line protocol will go down. The correct fix is to configure both sides with the same duplex and speed settings, preferably using auto-negotiation or manually setting both to full-duplex. Distractor A is wrong because no errors are present; D is wrong because the interface is up; C is wrong because the interface is not in err-disabled state.
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.
- ✗
Replace the Ethernet cable because it is faulty.
Why it's wrong here
No cable errors are reported (no CRC, runts, giants, or collisions), so the cable is likely not the issue.
- ✓
Configure both interfaces with the same duplex and speed settings, either both auto or both manually set to full-duplex and 1000 Mbps.
Why this is correct
The line protocol being down with up/up on the remote suggests a duplex mismatch, which can occur when one side is manually set and the other is auto-negotiating. Setting both sides consistently resolves the issue.
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.
- ✗
Issue the 'shutdown' and 'no shutdown' commands on the interface to recover from err-disabled state.
Why it's wrong here
The interface is not in err-disabled state; it shows 'up, line protocol is down'.
- ✗
Check the VLAN configuration on SwitchA because the interface is administratively down.
Why it's wrong here
The interface status is 'up', not 'administratively down', so the VLAN configuration is not the primary issue.
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.
✓Configure both interfaces with the same duplex and speed settings, either both auto or both manually set to full-duplex and 1000 Mbps.Correct answer▾
Why this is correct
The line protocol being down with up/up on the remote suggests a duplex mismatch, which can occur when one side is manually set and the other is auto-negotiating. Setting both sides consistently resolves the issue.
✗Replace the Ethernet cable because it is faulty.Wrong answer — click to see why▾
Why this is wrong here
The exhibit shows 0 input errors and 0 output errors, indicating the cable is probably good.
✗Issue the 'shutdown' and 'no shutdown' commands on the interface to recover from err-disabled state.Wrong answer — click to see why▾
Why this is wrong here
Err-disabled would show as 'err-disabled' in the interface status, which is not the case here.
✗Check the VLAN configuration on SwitchA because the interface is administratively down.Wrong answer — click to see why▾
Why this is wrong here
The line protocol is down due to Layer 2 issues, not because the interface is disabled or VLAN mismatch.
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
The interface is not in err-disabled state; it shows 'up, line protocol is down'.
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.
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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: Configure both interfaces with the same duplex and speed settings, either both auto or both manually set to full-duplex and 1000 Mbps. — The interface on SwitchA is up but the line protocol is down, indicating a Layer 1 (physical) issue but Layer 2 is not operational. The key clue is that the interface is set to full-duplex and 1000Mb/s, but there are no errors. However, the problem is that the interface speed is manually configured to 1000 Mbps, but the cable or the remote switch may not support gigabit speeds, or the remote interface is configured differently. In this scenario, the most common cause is a duplex mismatch: if SwitchB's interface is set to auto-negotiate and defaults to half-duplex due to a negotiation failure, the line protocol will go down. The correct fix is to configure both sides with the same duplex and speed settings, preferably using auto-negotiation or manually setting both to full-duplex. Distractor A is wrong because no errors are present; D is wrong because the interface is up; C is wrong because the interface is not in err-disabled state.
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.
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