Question 1,102 of 1,819
Switching and Network AccesshardMultiple ChoiceObjective-mapped

LACP 'on' Mode Mismatch: Why Interfaces Are Suspended

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. 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.

Network Topology
+SwitchA# show etherchannel summaryH - Hot-standby (LACP only)u - unsuitable for bundlingd - default portNumber of aggregators: 1Group Port-channel Protocol Ports

Two switches are connected using four Gigabit Ethernet interfaces configured as an EtherChannel with LACP. The network administrator notices that only two of the four interfaces are active in the port-channel, and the other two are in a suspended state. Upon further investigation, the administrator finds that the two inactive interfaces correspond to remote interfaces that are configured with the 'on' mode, while the active ones correspond to remote interfaces configured with LACP active/passive. The administrator also verifies that all local interfaces have the same speed, duplex, and VLAN. What is the most likely cause of the suspended interfaces?

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.

Network Topology
+SwitchA# show etherchannel summaryH - Hot-standby (LACP only)u - unsuitable for bundlingd - default portNumber of aggregators: 1Group Port-channel Protocol Ports

Quick Answer

The answer is that the suspended interfaces are caused by a mismatch where the remote switch ports are configured with the 'on' mode for EtherChannel instead of LACP active or passive. This is correct because LACP relies on the exchange of Link Aggregation Control Protocol Data Units (LACPDUs) to negotiate and maintain a port-channel; the 'on' mode creates a static EtherChannel that does not send or process LACPDUs, so the local LACP-enabled interfaces never receive the expected negotiation frames and are placed into a suspended state to prevent traffic loops or misforwarding. On the CCNA 200-301 v2 exam, this scenario tests your understanding of EtherChannel modes and the critical requirement that both sides of a link must agree on the protocol—a common trap is assuming 'on' mode works with LACP, when in fact it only pairs with another 'on' mode interface. Remember the memory tip: "Active or Passive for LACP to pass; 'on' is a lonely static song."

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 remote switch interfaces corresponding to the suspended local interfaces are configured with the 'on' mode instead of 'active' or 'passive' for LACP.

LACP requires both ends of a link to be configured in either 'active' or 'passive' mode to negotiate an EtherChannel. If some remote interfaces are set to 'on' mode (static EtherChannel), LACP negotiation fails on those links, causing the corresponding local LACP-enabled interfaces to remain in a suspended state. The local switch detects that LACP PDUs are not received on those interfaces and suspends them to prevent misconfiguration. The other two interfaces with correctly configured remote peers form the EtherChannel successfully.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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 interfaces are in err-disabled state due to a spanning-tree loop.

    Why it's wrong here

    The output shows 's' for suspended, not 'err-disabled'. Err-disabled would show 'D' or 'err-disabled' in the output.

  • The remote switch interfaces corresponding to the suspended local interfaces are configured with the 'on' mode instead of 'active' or 'passive' for LACP.

    Why this is correct

    When one switch has LACP active/passive and the other has 'on' (static), LACP negotiation fails, and the ports become suspended. Changing the remote switch to 'active' or 'passive' allows LACP to negotiate and bundle the ports.

    Clue confirmation

    The clue word "most likely" in the question point toward this answer.

    Related concept

    Read the scenario before looking for a memorised answer.

  • The port-channel interface is shutdown.

    Why it's wrong here

    If the port-channel interface were shutdown, all member interfaces would show 'D' (down) or 's' but the port-channel itself would show 'SD' or 'D'. The output shows Po1(SU), meaning the port-channel is up and in use.

  • There is a mismatch in the allowed VLANs on the member interfaces.

    Why it's wrong here

    While VLAN mismatch can cause issues, it typically results in the interfaces being in a different state, such as 'D' or 'I', not 's'. Also, the scenario states VLANs are the same.

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 remote switch interfaces corresponding to the suspended local interfaces are configured with the 'on' mode instead of 'active' or 'passive' for LACP.Correct answer

Why this is correct

When one switch has LACP active/passive and the other has 'on' (static), LACP negotiation fails, and the ports become suspended. Changing the remote switch to 'active' or 'passive' allows LACP to negotiate and bundle the ports.

The interfaces are in err-disabled state due to a spanning-tree loop.Wrong answer — click to see why

Why this is wrong here

The exhibit shows the ports as suspended, not err-disabled. Spanning-tree loops typically cause err-disable, not suspension.

The port-channel interface is shutdown.Wrong answer — click to see why

Why this is wrong here

The port-channel is up (U), so it is not shutdown.

There is a mismatch in the allowed VLANs on the member interfaces.Wrong answer — click to see why

Why this is wrong here

The scenario explicitly states that all interfaces are configured with the same VLAN, so this is not the 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: answer the scenario, not the keyword

Cisco often tests the misconception that all interfaces must match in speed, duplex, and VLAN to form an EtherChannel, but the trap here is that the LACP mode mismatch (active/passive vs. on) is the specific cause of suspended interfaces even when other parameters are consistent.

Trap categories for this question

  • Command / output trap

    The output shows 's' for suspended, not 'err-disabled'. Err-disabled would show 'D' or 'err-disabled' in the output.

  • Scenario analysis trap

    While VLAN mismatch can cause issues, it typically results in the interfaces being in a different state, such as 'D' or 'I', not 's'. Also, the scenario states VLANs are the same.

Detailed technical explanation

How to think about this question

LACP uses the Link Aggregation Control Protocol (IEEE 802.3ad) to exchange LACPDUs between switches. When one side is configured with 'active' or 'passive' and the other with 'on', no LACPDUs are exchanged, so the LACP-enabled side marks its interfaces as 'suspended' because it cannot establish a valid LACP negotiation. In a real-world scenario, this often happens when a network engineer forgets to change the default mode on one switch or mixes static and dynamic configurations.

KKey Concepts to Remember

  • Read the scenario before looking for a memorised answer.
  • Find the constraint that changes the correct option.
  • Eliminate answers that are true in general but not in this case.

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

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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.

Visual reference

Switch VLAN 10 Sales (192.168.10.0/24) PC-A PC-B VLAN 20 HR (192.168.20.0/24) PC-C PC-D Router VLANs isolate traffic — inter-VLAN routing requires a Layer 3 device

What to study next

Got this wrong? Here's your next step.

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FAQ

Questions learners often ask

What does this 200-301 question test?

Switching and Network Access — This question tests Switching and Network Access — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The remote switch interfaces corresponding to the suspended local interfaces are configured with the 'on' mode instead of 'active' or 'passive' for LACP. — LACP requires both ends of a link to be configured in either 'active' or 'passive' mode to negotiate an EtherChannel. If some remote interfaces are set to 'on' mode (static EtherChannel), LACP negotiation fails on those links, causing the corresponding local LACP-enabled interfaces to remain in a suspended state. The local switch detects that LACP PDUs are not received on those interfaces and suspends them to prevent misconfiguration. The other two interfaces with correctly configured remote peers form the EtherChannel successfully.

What should I do if I get this 200-301 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jun 11, 2026

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