CCNA Switching and Network Access Practice Question
This 200-301 practice question tests your understanding of switching and network access. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: etherChannel bundles multiple physical links into a single logical link to increase bandwidth and provide redundancy between switches.. 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
Group Port-channel Protocol Ports
1 Po1(SU) LACP Gi1/0/1(P) Gi1/0/2(s)
Two switches are bundled with LACP, but only one physical link is forwarding traffic in the port-channel. What is the most likely reason?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
One member interface has a trunk configuration mismatch
For an EtherChannel to form correctly, the member interfaces must match on key settings such as speed, duplex, trunking, and allowed VLAN list. A mismatch keeps one link from bundling even if LACP is enabled on both sides.
Key principle: EtherChannel bundles multiple physical links into a single logical link to increase bandwidth and provide redundancy between 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.
✓
One member interface has a trunk configuration mismatch
Why this is correct
A mismatch in Layer 2 settings is a classic reason a link is suspended or left out of the channel.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
EtherChannel bundles multiple physical links into a single logical link to increase bandwidth and provide redundancy between switches.
✗
LACP requires exactly one active and one passive side only
This would be correct if the question stated that LACP is configured with both sides set to passive, causing the bundle to fail to form because neither side initiates negotiation. In that scenario, no links would be active, not just one.
✗
STP blocks all but one interface inside every EtherChannel
In a scenario where multiple physical links are bundled without EtherChannel (e.g., using STP for redundancy), STP would block all but one interface to prevent loops.
A question might ask: 'Which of the following is a limitation of EtherChannel?' and list options including 'EtherChannel cannot be used on trunk ports' as a distractor. In that context, it would be incorrect, but if the question were 'Which of the following is NOT a valid EtherChannel configuration?' and the correct answer was 'EtherChannel on trunk ports', then this option would be wrong. However, for it to be correct, the question would need to explicitly state that trunk ports are not supported, which is false in real-world scenarios.
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.
✓One member interface has a trunk configuration mismatchCorrect answer▾
Why this is correct
A mismatch in Layer 2 settings is a classic reason a link is suspended or left out of the channel.
✗LACP requires exactly one active and one passive side onlyWrong answer — click to see why▾
Why this is wrong here
LACP supports active-active mode where both sides are configured as active, which is a common and valid configuration. The statement that LACP requires exactly one active and one passive side is incorrect; active-passive is just one possible combination.
★ When this WOULD be the correct answer
This would be correct if the question stated that LACP is configured with both sides set to passive, causing the bundle to fail to form because neither side initiates negotiation. In that scenario, no links would be active, not just one.
Why candidates choose this
Students often confuse LACP with PAgP, which does require one side to be desirable (active) and the other to be auto (passive) in certain modes, or they may think that LACP requires a negotiation handshake with one side initiating.
✗STP blocks all but one interface inside every EtherChannelWrong answer — click to see why▾
Why this is wrong here
STP treats the entire EtherChannel as a single logical interface, so it does not block individual member links. STP will only block the port-channel itself if there is a loop, but it does not block all but one interface inside the channel.
★ When this WOULD be the correct answer
In a scenario where multiple physical links are bundled without EtherChannel (e.g., using STP for redundancy), STP would block all but one interface to prevent loops.
Why candidates choose this
Students might think that STP operates on each physical link independently within an EtherChannel, not realizing that the channel is a logical bundle. They may also confuse STP behavior with load-balancing algorithms that might not use all links equally.
✗EtherChannel cannot be used on trunk portsWrong answer — click to see why▾
Why this is wrong here
EtherChannel is commonly used on trunk ports to increase bandwidth and provide redundancy between switches. There is no restriction that prevents EtherChannel from being used on trunk ports; in fact, it is a best practice for inter-switch links.
★ When this WOULD be the correct answer
A question might ask: 'Which of the following is a limitation of EtherChannel?' and list options including 'EtherChannel cannot be used on trunk ports' as a distractor. In that context, it would be incorrect, but if the question were 'Which of the following is NOT a valid EtherChannel configuration?' and the correct answer was 'EtherChannel on trunk ports', then this option would be wrong. However, for it to be correct, the question would need to explicitly state that trunk ports are not supported, which is false in real-world scenarios.
Why candidates choose this
Students might think that trunk ports have special VLAN tagging that could interfere with EtherChannel hashing or load balancing, or they may confuse EtherChannel with access port configurations.
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
Be careful not to confuse individual link issues with overall port-channel configuration problems. Ensure all settings match across member interfaces.
Detailed technical explanation
How to think about this question
EtherChannel is a technology that aggregates multiple physical Ethernet links into a single logical link, increasing bandwidth and providing redundancy between switches. Cisco supports EtherChannel using protocols like LACP, which dynamically negotiates the aggregation by exchanging protocol packets to ensure both ends agree on the channel parameters. This bundling allows traffic to be load-balanced across the member links while presenting a single logical interface to higher layers.
For an EtherChannel to form correctly, all member interfaces must have identical Layer 2 configurations, including speed, duplex, trunking mode, and allowed VLAN lists. LACP uses these parameters to verify compatibility; if any mismatch exists, LACP will suspend the problematic link from the port-channel, causing only the correctly configured links to forward traffic. This behavior prevents network loops and inconsistent forwarding states.
A common exam trap is assuming that STP blocks individual member links inside an EtherChannel or that LACP requires one side to be passive. In reality, STP treats the entire port-channel as a single logical interface, so it does not block individual links. Also, LACP supports active-active negotiation on both sides. The practical impact is that a single link not forwarding usually signals a configuration mismatch, such as a trunk VLAN mismatch, rather than protocol or STP behavior.
KKey Concepts to Remember
EtherChannel bundles multiple physical links into a single logical link to increase bandwidth and provide redundancy between switches.
LACP (Link Aggregation Control Protocol) dynamically negotiates and manages EtherChannel member interfaces to ensure consistent configuration and link compatibility.
All member interfaces in an EtherChannel must match in key Layer 2 parameters such as speed, duplex, trunk mode, and allowed VLANs for the channel to form correctly.
A mismatch in trunk configuration, such as differing allowed VLAN lists or trunk modes, causes LACP to suspend the affected member interface from forwarding traffic.
STP (Spanning Tree Protocol) treats an EtherChannel as a single logical port and does not block individual member links inside the port-channel.
LACP supports active-active mode where both sides actively negotiate the channel, not requiring one side to be passive and the other active.
EtherChannel can be configured on trunk ports, allowing multiple VLANs to be carried over the aggregated links without issue.
When one physical link in an EtherChannel is not forwarding traffic, it usually indicates a configuration mismatch rather than a protocol limitation or STP blocking.
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
EtherChannel bundles multiple physical links into a single logical link to increase bandwidth and provide redundancy between 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review etherChannel bundles multiple physical links into a single logical link to increase bandwidth and provide redundancy between switches., then practise related 200-301 questions on the same topic to reinforce the concept.
Switching and Network Access — This question tests Switching and Network Access — EtherChannel bundles multiple physical links into a single logical link to increase bandwidth and provide redundancy between switches..
What is the correct answer to this question?
The correct answer is: One member interface has a trunk configuration mismatch — For an EtherChannel to form correctly, the member interfaces must match on key settings such as speed, duplex, trunking, and allowed VLAN list. A mismatch keeps one link from bundling even if LACP is enabled on both sides.
What should I do if I get this 200-301 question wrong?
Review etherChannel bundles multiple physical links into a single logical link to increase bandwidth and provide redundancy between switches., then practise related 200-301 questions on the same topic to reinforce the concept.
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?
EtherChannel bundles multiple physical links into a single logical link to increase bandwidth and provide redundancy between switches.
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