The answer is an EtherChannel mode mismatch, where one side is using LACP active while the other is set to on. This fails because LACP active mode actively sends negotiation packets to form the bundle, whereas the on mode forces the interface into a static EtherChannel without any negotiation protocol, so the two sides never agree on a common configuration and the bundle remains down. On the CCNA 200-301 v2 exam, this question tests your understanding of EtherChannel negotiation modes—specifically that both ends must use either LACP (active/passive) or PAgP (desirable/auto), or both be set to on, but never a mix of a negotiation protocol and static mode. A common trap is confusing switch priority or VLAN settings with EtherChannel formation, but remember: the native VLAN only needs to match, not be VLAN 1, and all member interfaces must share the same VLAN. For a quick memory tip, think “active talks, on walks”—if one side negotiates and the other doesn’t, the link stays down.
CCNA Switching and Network Access Practice Question
This 200-301 practice question tests your understanding of switching and network access. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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(SD) LACP Gi1/0/1(I) Gi1/0/2(I)
SW1 interface range gi1/0/1-2
channel-group 1 mode active
SW2 interface range gi1/0/1-2
channel-group 1 mode on
An administrator configures an EtherChannel between SW1 and SW2. The port-channel interfaces are physically up, but the EtherChannel bundle fails to come up. On SW1, the channel-group is set to mode active; on SW2, it is set to mode on. What is the most likely cause?
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.
SW1# show etherchannel summary
Group Port-channel Protocol Ports
1 Po1(SD) LACP Gi1/0/1(I) Gi1/0/2(I)
SW1 interface range gi1/0/1-2
channel-group 1 mode active
SW2 interface range gi1/0/1-2
channel-group 1 mode on
A
The switch priority values are mismatched
Why wrong: Priority can affect STP, not whether LACP negotiates with mode on.
B
One side is using LACP active while the other side is set to on
Mode on does not negotiate LACP.
C
The native VLAN must be VLAN 1 for EtherChannel to form
Why wrong: That is not a requirement.
D
Gi1/0/2 cannot be bundled because interfaces must be in different VLANs
Why wrong: Bundled links must be configured consistently, not differently.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
One side is using LACP active while the other side is set to on
EtherChannel requires compatible modes: LACP active mode sends negotiation packets, while 'on' mode disables all negotiation, so the two sides cannot agree and the bundle stays down. Option A is wrong because switch priority values are used in STP root election, not EtherChannel formation. Option C is wrong because the native VLAN does not need to be VLAN 1; it only needs to match on both ends. Option D is wrong because all member interfaces in an EtherChannel must be in the same VLAN, not different ones.
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.
✗
The switch priority values are mismatched
Why it's wrong here
Priority can affect STP, not whether LACP negotiates with mode on.
✓
One side is using LACP active while the other side is set to on
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.
✗
The native VLAN must be VLAN 1 for EtherChannel to form
Why it's wrong here
That is not a requirement.
✗
Gi1/0/2 cannot be bundled because interfaces must be in different VLANs
Why it's wrong here
Bundled links must be configured consistently, not differently.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Ensure both sides of an EtherChannel are set to compatible modes; 'on' mode does not participate in LACP negotiation.
Detailed technical explanation
How to think about this question
EtherChannel is a technology that aggregates multiple physical Ethernet links into a single logical link to increase bandwidth and provide redundancy. Cisco supports EtherChannel using protocols like LACP and PAgP, or by forcing the channel with the 'mode on' setting. LACP uses negotiation modes—active and passive—to dynamically detect and form EtherChannel bundles. Active mode actively initiates negotiation, while passive mode only responds to negotiation requests. The 'mode on' setting disables negotiation and forces the link to bundle without protocol exchange.
For EtherChannel to form successfully, both ends must agree on key parameters including speed, duplex, allowed VLANs, and most importantly, the channel mode. If one side is set to LACP active and the other side is set to 'mode on', the side using 'on' does not participate in LACP negotiation. This mismatch causes the LACP side to wait for negotiation responses that never arrive, preventing the EtherChannel bundle from coming up. Both sides must either use compatible LACP modes (active/passive) or both be set to 'on' to force the bundle.
A common exam trap is confusing the 'mode on' setting with LACP active or passive modes. Candidates may incorrectly assume that 'mode on' will negotiate with LACP active, but it does not. This leads to EtherChannel failure and a down port-channel interface. In practical networks, mismatched channel modes cause troubleshooting challenges, as the physical links appear connected but the logical bundle never forms, impacting redundancy and bandwidth aggregation benefits.
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) uses negotiation modes such as active and passive to dynamically form EtherChannel bundles.
The 'mode on' setting forces EtherChannel without negotiation, requiring both sides to be set to 'on' for the bundle to come up.
Both ends of an EtherChannel must have matching channel modes; mismatched modes like 'active' and 'on' prevent successful negotiation.
EtherChannel requires consistent configuration of speed, duplex, allowed VLANs, and channel protocol on all member interfaces.
Native VLAN mismatches do not prevent EtherChannel formation but can cause VLAN tagging issues and traffic problems.
Switch priority values affect Spanning Tree Protocol (STP) roles but do not impact EtherChannel negotiation or formation.
Interfaces bundled in EtherChannel must have consistent VLAN membership; interfaces in different VLANs cannot be bundled together.
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 side is using LACP active while the other side is set to on — EtherChannel requires compatible modes: LACP active mode sends negotiation packets, while 'on' mode disables all negotiation, so the two sides cannot agree and the bundle stays down. Option A is wrong because switch priority values are used in STP root election, not EtherChannel formation. Option C is wrong because the native VLAN does not need to be VLAN 1; it only needs to match on both ends. Option D is wrong because all member interfaces in an EtherChannel must be in the same VLAN, not different ones.
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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