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Switching and Network AccesshardTroubleshootingObjective-mapped

CCNA Switching and Network Access Practice Question

Network Topology
+interface GigabitEthernet0/1switchport mode accessswitchport access vlan 100speed 1000duplex fullchannel-group 1 mode activeinterface GigabitEthernet0/2interface Port-channel1SW1# show etherchannel summaryH - Hot-standby (LACP only)u - unsuitable for bundlingd - default portNumber of aggregators: 1Group Port-channel Protocol Ports1 Po1(SD) LACP Gi0/1(P) Gi0/2(D)Full-duplex, 1000Mb/s

You are connected to SW1. Configure an LACP EtherChannel between SW1 and SW2 using interfaces GigabitEthernet0/1 and GigabitEthernet0/2. Set the channel-group mode to active on both switches. Verify that the port-channel interface is configured with VLAN 100 as an access port. Then, troubleshoot and fix the issue that prevents the EtherChannel from forming due to a mismatched speed on one of the member links. After correction, verify the EtherChannel is up with 'show etherchannel summary'.

⚠ Common exam trap

Do not confuse LACP modes (active/passive) with PAgP modes (desirable/auto). Also, remember that physical parameters like speed and duplex must match across all member ports; logical configurations like VLAN or trunking are separate but must also be consistent. Always verify the root cause before changing unrelated settings.

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

Set speed 1000 and duplex full on interface GigabitEthernet0/2 of SW1, ensuring the corresponding interface on SW2 has matching settings, then verify with 'show etherchannel summary'.

The EtherChannel fails because interface GigabitEthernet0/2 on SW1 has a mismatched speed (likely 100 Mbps) compared to the other member link (1000 Mbps). LACP requires all member ports to have identical speed and duplex. The solution is to set the speed on Gi0/2 to 1000 and duplex to full. After correction, the port will bundle, and the port-channel will come up. Verification with 'show etherchannel summary' should show both ports as 'P' (bundled) and the port-channel as 'SU' (in use, Layer2).

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • Set speed 1000 and duplex full on interface GigabitEthernet0/2 of SW1, ensuring the corresponding interface on SW2 has matching settings, then verify with 'show etherchannel summary'.

    Why this is correct

    The EtherChannel fails because interface GigabitEthernet0/2 on SW1 has a mismatched speed (likely 100 Mbps) compared to the other member link (1000 Mbps). LACP requires all member ports to have identical speed and duplex. The solution is to set the speed on Gi0/2 to 1000 and duplex to full on SW1, and ensure SW2's Gi0/2 is also set to 1000/full. After correction, the port will bundle, and the port-channel will come up. Verification with 'show etherchannel summary' should show both ports as 'P' (bundled) and the port-channel as 'SU' (in use, Layer2).

  • Change the channel-group mode to desirable on both switches and verify with 'show etherchannel summary'.

    Why it's wrong here

    This is incorrect because the mode 'desirable' is a PAgP mode, not LACP. The question specifies LACP, which uses modes 'active' and 'passive'. Changing to 'desirable' would not resolve the speed mismatch and would use the wrong protocol.

  • Remove the access VLAN configuration from the port-channel interface and configure it as a trunk port instead.

    Why it's wrong here

    This is incorrect because the issue is a speed mismatch, not a VLAN or trunking configuration. The port-channel is intended to be an access port in VLAN 100, and changing it to a trunk would not fix the speed mismatch. The EtherChannel would still fail to form due to inconsistent speeds.

  • Configure the channel-group mode to passive on SW1 and active on SW2, then verify with 'show etherchannel summary'.

    Why it's wrong here

    This is incorrect because while LACP allows mixed modes (active/passive), the question states both switches are set to active. Changing one to passive would not fix the speed mismatch; the EtherChannel would still fail because the ports have different speeds. Additionally, both sides must have compatible modes, but the mismatch is physical, not protocol.

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.

Set speed 1000 and duplex full on interface GigabitEthernet0/2 of SW1, ensuring the corresponding interface on SW2 has matching settings, then verify with 'show etherchannel summary'.Correct answer

Why this is correct

The EtherChannel fails because interface GigabitEthernet0/2 on SW1 has a mismatched speed (likely 100 Mbps) compared to the other member link (1000 Mbps). LACP requires all member ports to have identical speed and duplex. The solution is to set the speed on Gi0/2 to 1000 and duplex to full on SW1, and ensure SW2's Gi0/2 is also set to 1000/full. After correction, the port will bundle, and the port-channel will come up. Verification with 'show etherchannel summary' should show both ports as 'P' (bundled) and the port-channel as 'SU' (in use, Layer2).

Change the channel-group mode to desirable on both switches and verify with 'show etherchannel summary'.Wrong answer — click to see why

Why this is wrong here

The specific factual error is that 'desirable' is a PAgP mode, not LACP. LACP uses 'active' and 'passive' modes.

Why candidates choose this

Candidates may confuse PAgP and LACP modes, especially since 'desirable' is a common PAgP mode that initiates negotiation, similar to LACP 'active'.

Remove the access VLAN configuration from the port-channel interface and configure it as a trunk port instead.Wrong answer — click to see why

Why this is wrong here

The specific factual error is that the problem is physical (speed mismatch), not logical (VLAN/trunking). Changing the port type does not address the root cause.

Why candidates choose this

Candidates might think that VLAN mismatches or trunking issues are common EtherChannel problems, but in this scenario, the speed mismatch is the explicit issue.

Configure the channel-group mode to passive on SW1 and active on SW2, then verify with 'show etherchannel summary'.Wrong answer — click to see why

Why this is wrong here

The specific factual error is that the speed mismatch is the root cause, not the LACP mode. Even with correct modes, the EtherChannel will not form if speeds differ.

Why candidates choose this

Candidates may think that LACP mode negotiation is the issue, especially if they recall that both sides need to be in active or one active and one passive. However, the speed mismatch overrides this.

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?”

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

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Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

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