Question 1hardmultiple choice
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Question 1,153 of 1,052
hardmultiple choiceObjective-mapped
CCNA Practice Question: A network technician connects a new Cisco switch…
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
SwitchA# show interfaces gigabitethernet 0/1
GigabitEthernet0/1 is down, line protocol is down (err-disabled)
Hardware is Gigabit Ethernet, address is 0011.2233.4455 (bia 0011.2233.4455)
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)
Auto-duplex, Auto-speed, 1000BaseTX/FX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output never, 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 multicast)
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 out
SwitchA# show errdisable detect
ErrDisable Reason Detection Status
------------------ -----------------
udld Enabled
bpduguard Enabled
security-violation Enabled
SwitchA# show interfaces gigabitethernet 0/1 status
Port Name Status Vlan Duplex Speed Type
Gi0/1 err-disabled 1 auto auto 10/100/1000BaseTXA network technician connects a new Cisco switch to an existing access switch using a Category 5e copper patch cable. The link fails to come up, and the interface status shows 'err-disabled'. The technician checks the interface diagnostics and the running configuration. What is the most likely cause of the problem?
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 the interface as a trunk port and disable spanning-tree BPDU guard.
The interface is in err-disabled state, and 'show errdisable detect' shows that bpduguard is enabled as an errdisable detection cause. BPDU guard is typically enabled on access ports to protect against loops from unauthorized switches. If a switch is connected to a port configured with spanning-tree portfast and bpduguard, the port will go into err-disabled state upon receiving a BPDU from the other switch. The correct action is to either disable bpduguard on the port or configure the port as a trunk if the connection is intentional. The other options are incorrect because the cable type (Cat5e) supports 1000BASE-T at 100m, the SFP is not used for copper RJ-45 ports, and speed/duplex mismatch would show as line protocol down but not necessarily err-disabled.
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 Category 5e cable with a Category 6 cable to support Gigabit Ethernet.
Why it's wrong here
Category 5e cable is fully capable of supporting 1000BASE-T (Gigabit Ethernet) up to 100 meters, so a cable upgrade is not necessary.
- ✓
Configure the interface as a trunk port and disable spanning-tree BPDU guard.
Why this is correct
The port is in err-disabled because bpduguard is enabled. Since this is a connection between two switches, the port should be configured as a trunk (or at least not as an access port with portfast) and bpduguard should be disabled to prevent the errdisable state.
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.
- ✗
Replace the copper SFP with a fiber SFP to increase the distance.
Why it's wrong here
The interface diagnostics show the port type is 10/100/1000BaseTX (copper RJ-45), not an SFP slot. The problem is not related to distance or transceiver type.
- ✗
Manually set the speed and duplex to 1000 Mbps and full duplex on both switches.
Why it's wrong here
While speed/duplex mismatch can cause interface issues, the err-disabled state with bpduguard enabled indicates a BPDU guard violation, not a mismatch. The interface shows auto-negotiation is enabled.
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 the interface as a trunk port and disable spanning-tree BPDU guard.Correct answer▾
Why this is correct
The port is in err-disabled because bpduguard is enabled. Since this is a connection between two switches, the port should be configured as a trunk (or at least not as an access port with portfast) and bpduguard should be disabled to prevent the errdisable state.
✗Replace the Category 5e cable with a Category 6 cable to support Gigabit Ethernet.Wrong answer — click to see why▾
Why this is wrong here
The symptom is err-disabled, not a speed or duplex mismatch; cable type is not the issue.
✗Replace the copper SFP with a fiber SFP to increase the distance.Wrong answer — click to see why▾
Why this is wrong here
The port is a built-in copper port, not an SFP-based interface; distance is not the issue.
✗Manually set the speed and duplex to 1000 Mbps and full duplex on both switches.Wrong answer — click to see why▾
Why this is wrong here
The err-disabled state is due to BPDU guard, not speed/duplex mismatch; manual settings would not fix the root cause.
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 diagnostics show the port type is 10/100/1000BaseTX (copper RJ-45), not an SFP slot. The problem is not related to distance or transceiver type.
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 the interface as a trunk port and disable spanning-tree BPDU guard. — The interface is in err-disabled state, and 'show errdisable detect' shows that bpduguard is enabled as an errdisable detection cause. BPDU guard is typically enabled on access ports to protect against loops from unauthorized switches. If a switch is connected to a port configured with spanning-tree portfast and bpduguard, the port will go into err-disabled state upon receiving a BPDU from the other switch. The correct action is to either disable bpduguard on the port or configure the port as a trunk if the connection is intentional. The other options are incorrect because the cable type (Cat5e) supports 1000BASE-T at 100m, the SFP is not used for copper RJ-45 ports, and speed/duplex mismatch would show as line protocol down but not necessarily err-disabled.
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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