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Switching and Network AccesshardTroubleshootingObjective-mapped

CCNA Switching and Network Access Practice Question

Network Topology
Gi0/1-4Gi0/1-44x linksSW1SW2

You are connected to SW1. Two switches, SW1 and SW2, are connected via four GigabitEthernet links. Configure LACP EtherChannel between them using interfaces GigabitEthernet0/1 through GigabitEthernet0/4 on SW1. Set the channel-group mode to active on SW1. The port-channel interface must be configured as a trunk, allowing VLANs 10, 20, 30. However, the EtherChannel is not forming. The current configuration is shown below. Identify and fix the issue, then verify the EtherChannel is operational.

⚠ Common exam trap

The exam trap is that candidates often focus on LACP modes or trunk negotiation but overlook the Layer 2/Layer 3 mismatch between the port-channel interface and member interfaces. Always ensure the port-channel interface is configured as either Layer 2 or Layer 3 to match the member ports.

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

Remove 'no switchport' and IP address from Port-channel1, then configure 'switchport mode trunk' and 'switchport trunk allowed vlan 10,20,30'.

The EtherChannel is not forming because the Port-channel1 interface is configured as a Layer 3 interface (no switchport, IP address), while the member interfaces are Layer 2 switchports (switchport mode trunk). This mismatch prevents the channel from bundling. To fix this, configure Port-channel1 as a Layer 2 trunk interface with the same allowed VLANs. The solution: remove the no switchport command and the IP address, then apply switchport mode trunk and switchport trunk allowed vlan 10,20,30. After correction, the ports should bundle and the show etherchannel summary will show the ports as bundled (P) and the port-channel as Layer 2 (S).

Answer analysis

Option-by-option breakdown

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

  • Remove 'no switchport' and IP address from Port-channel1, then configure 'switchport mode trunk' and 'switchport trunk allowed vlan 10,20,30'.

    Why this is correct

    The EtherChannel fails because Port-channel1 is configured as a Layer 3 interface (no switchport, IP address) while the member ports are Layer 2 switchports. This mismatch prevents bundling. Converting Port-channel1 to a Layer 2 trunk with the same allowed VLANs resolves the issue.

  • Change the channel-group mode on the member interfaces from active to passive.

    Why it's wrong here

    This is incorrect because the mode mismatch is not the issue; both sides can use active mode. Changing to passive would still work if the other side is active, but it does not fix the Layer 2/Layer 3 mismatch.

  • Add the 'switchport nonegotiate' command to the member interfaces.

    Why it's wrong here

    Adding 'switchport nonegotiate' to the member interfaces disables Dynamic Trunking Protocol (DTP) on those ports, which only stops automatic trunk negotiation. It does nothing to align the Layer 3 nature of Port-channel1 (configured with 'no switchport' and an IP address) with the Layer 2 member switchports. The EtherChannel fails because the port-channel interface itself is a routed interface while the members are Layer 2 switchports; without converting the port-channel to Layer 2 trunk mode, this command cannot resolve the mismatch.

  • Configure the member interfaces with 'channel-group 1 mode on' instead of active.

    Why it's wrong here

    Changing the channel-group mode from 'active' to 'on' forces the EtherChannel to form without LACP negotiation, bypassing the protocol-state check. However, 'mode on' does not alter the fundamental Layer 2/Layer 3 incompatibility: the member interfaces are Layer 2 switchports, whereas Port-channel1 has been configured as a Layer 3 interface with 'no switchport' and an IP address. The switch still enforces interface-layer consistency for bundling, so even forced mode fails until the port-channel is changed to a Layer 2 trunk.

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.

Remove 'no switchport' and IP address from Port-channel1, then configure 'switchport mode trunk' and 'switchport trunk allowed vlan 10,20,30'.Correct answer

Why this is correct

The EtherChannel fails because Port-channel1 is configured as a Layer 3 interface (no switchport, IP address) while the member ports are Layer 2 switchports. This mismatch prevents bundling. Converting Port-channel1 to a Layer 2 trunk with the same allowed VLANs resolves the issue.

Change the channel-group mode on the member interfaces from active to passive.Wrong answer — click to see why

Why this is wrong here

The specific factual error: The problem is a Layer 2/Layer 3 mismatch, not the LACP mode. Active mode is valid and commonly used.

Why candidates choose this

Candidates might think that LACP negotiation requires one side active and one passive, but active-active is also valid. They may overlook the port-channel interface configuration.

Add the 'switchport nonegotiate' command to the member interfaces.Wrong answer — click to see why

Why this is wrong here

The specific factual error: 'switchport nonegotiate' affects trunk negotiation, not EtherChannel bundling.

Why candidates choose this

Candidates may confuse DTP with LACP or think that disabling negotiation helps, but it does not address the root cause.

Configure the member interfaces with 'channel-group 1 mode on' instead of active.Wrong answer — click to see why

Why this is wrong here

The specific factual error: The mode change does not fix the interface type mismatch; the port-channel must be Layer 2 to match the member ports.

Why candidates choose this

Candidates might think that using 'mode on' bypasses negotiation issues, but it does not resolve configuration inconsistencies between the port-channel and member interfaces.

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

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