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Question 593 of 1,052
hardmultiple choiceObjective-mapped
CCNA Practice Question: Is troubleshooting a connectivity issue between…
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
SW1# show etherchannel summary
Flags: D - down P - bundled in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3 S - Layer2
U - in use N - not in use, no aggregation
f - failed to allocate aggregator
M - not in use, no aggregation due to minimum links not met
m - not in use, port not aggregated due to minimum links not met
u - unsuitable for bundling
w - waiting to be aggregated
d - default port
Number of channel-groups in use: 1
Number of aggregators: 1
Group Port-channel Protocol Ports
------+-------------+-----------+-----------------------------------------------
1 Po1(SU) LACP Gi0/0/0(P) Gi0/0/1(P) Gi0/0/2(P) Gi0/0/3(I)A network engineer is troubleshooting a connectivity issue between two switches, SW1 and SW2, which are connected via four GigabitEthernet links configured as an LACP EtherChannel. Hosts on VLAN 10 connected to SW1 can ping the management IP of SW2, but cannot reach hosts on VLAN 10 connected to SW2. The engineer runs a show command on SW1. 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
✓
The interface Gi0/0/3 has a different LACP port priority or is configured with 'channel-group 1 mode passive' while the other ports use 'active'.
The 'I' flag on Gi0/0/3 indicates the port is in stand-alone mode, meaning it is not part of the EtherChannel. This can happen if LACP negotiation fails due to a mismatch in the LACP mode (active/passive) or a misconfiguration such as a different allowed VLAN list. Since three ports are bundled (P) and one is not (I), the channel is still up (SU), but the missing port reduces bandwidth and may cause instability. The correct fix is to ensure that Gi0/0/3 is configured with the same LACP mode and VLAN membership as the other ports. Options A, C, and D are incorrect because the port is not in err-disabled state, the port-channel is up, and there is no evidence of a spanning-tree blocking issue.
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.
- ✗
The interface Gi0/0/3 is in err-disabled state due to a spanning-tree BPDU guard violation.
Why it's wrong here
The 'I' flag stands for stand-alone, not err-disabled. An err-disabled interface would show as 'D' or 'err-disabled' in the output.
- ✓
The interface Gi0/0/3 has a different LACP port priority or is configured with 'channel-group 1 mode passive' while the other ports use 'active'.
Why this is correct
A mismatch in LACP mode (active vs. passive) or port priority can cause a port to remain in stand-alone mode. The 'I' flag indicates the port is not negotiating LACP successfully.
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.
- ✗
The port-channel interface is down (not in use), causing all member ports to be stand-alone.
Why it's wrong here
The port-channel is shown as 'SU' (Layer2, in use), so it is operational. The issue is only with one member port.
- ✗
The switch is running out of MAC addresses for the EtherChannel, so one port cannot be added.
Why it's wrong here
EtherChannel does not run out of MAC addresses; each port uses its own MAC. This is not a realistic failure scenario for LACP.
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.
✓The interface Gi0/0/3 has a different LACP port priority or is configured with 'channel-group 1 mode passive' while the other ports use 'active'.Correct answer▾
Why this is correct
A mismatch in LACP mode (active vs. passive) or port priority can cause a port to remain in stand-alone mode. The 'I' flag indicates the port is not negotiating LACP successfully.
✗The interface Gi0/0/3 is in err-disabled state due to a spanning-tree BPDU guard violation.Wrong answer — click to see why▾
Why this is wrong here
The output does not show err-disabled; the interface is in stand-alone mode.
✗The port-channel interface is down (not in use), causing all member ports to be stand-alone.Wrong answer — click to see why▾
Why this is wrong here
The port-channel is up; only one member is not bundled.
✗The switch is running out of MAC addresses for the EtherChannel, so one port cannot be added.Wrong answer — click to see why▾
Why this is wrong here
MAC address exhaustion is not a typical cause for a single port being stand-alone.
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 'I' flag stands for stand-alone, not err-disabled. An err-disabled interface would show as 'D' or 'err-disabled' in the output.
Scenario analysis trap
EtherChannel does not run out of MAC addresses; each port uses its own MAC. This is not a realistic failure scenario for LACP.
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: The interface Gi0/0/3 has a different LACP port priority or is configured with 'channel-group 1 mode passive' while the other ports use 'active'. — The 'I' flag on Gi0/0/3 indicates the port is in stand-alone mode, meaning it is not part of the EtherChannel. This can happen if LACP negotiation fails due to a mismatch in the LACP mode (active/passive) or a misconfiguration such as a different allowed VLAN list. Since three ports are bundled (P) and one is not (I), the channel is still up (SU), but the missing port reduces bandwidth and may cause instability. The correct fix is to ensure that Gi0/0/3 is configured with the same LACP mode and VLAN membership as the other ports. Options A, C, and D are incorrect because the port is not in err-disabled state, the port-channel is up, and there is no evidence of a spanning-tree blocking issue.
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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