CCNA Switching and Network Access Practice Question
Network Topology
You are connected to SW1. Configure an LACP EtherChannel between SW1 and SW2 using interfaces GigabitEthernet0/1 and GigabitEthernet0/2. The port-channel interface must be configured as a trunk allowing VLANs 10, 20, and 30. Currently, the channel is not forming due to a mismatch in speed/duplex and VLAN configuration on SW2. Troubleshoot and resolve the issue so that the EtherChannel comes up as a Layer 2 trunk.
⚠ Common exam trap
The exam trap is that candidates may focus solely on the speed/duplex mismatch and forget to verify the VLAN allowed list on the trunk. Also, they might incorrectly try to match by lowering SW1's settings instead of raising SW2's.
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
✓
On SW2, configure interfaces GigabitEthernet0/1 and 0/2 with speed 1000, duplex full, and on the port-channel interface, set allowed VLANs to 10,20,30.
The EtherChannel is not forming because SW2's interfaces have speed 100 and duplex half, while SW1's interfaces have speed 1000 and duplex full. Additionally, the allowed VLANs on SW2's trunk must include VLAN 30, and this should be configured on the port-channel interface, not the physical interfaces. To fix, on SW2, set the speed to 1000 and duplex to full on Gi0/1 and Gi0/2, then on the port-channel interface, configure allowed VLANs 10,20,30. After these changes, the channel will come up as a Layer 2 trunk.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
On SW2, configure interfaces GigabitEthernet0/1 and 0/2 with speed 1000, duplex full, and on the port-channel interface, set allowed VLANs to 10,20,30.
Why this is correct
Configuring both member interfaces with speed 1000 and duplex full matches SW1's negotiated physical parameters, which is mandatory for LACP to treat them as eligible for bundling into a single port-channel. Setting the allowed VLAN list to 10,20,30 on the port-channel interface ensures the aggregated trunk forwards exactly the required VLANs, consistent with SW1's configuration. This is the only configuration that satisfies both the physical-layer prerequisites and the logical trunking requirements, allowing the EtherChannel to form and carry the needed VLANs.
- ✗
On SW2, configure interfaces GigabitEthernet0/1 and 0/2 with speed 100, duplex half, and on the port-channel interface, set allowed VLANs to 10,20,30.
Why it's wrong here
Forcing the member interfaces to speed 100 and duplex half creates a speed and duplex mismatch with SW1's 1000/full settings, preventing LACP from successfully negotiating an EtherChannel. Even though the allowed VLAN list of 10,20,30 is correct, a link on either side that isn't configured with matching physical parameters will fail to join the bundle, leaving the port-channel down. Additionally, 100 Mbps half-duplex is rarely supported on modern Gigabit Ethernet interfaces and is not a valid alternative to the required full-duplex gigabit configuration.
- ✗
On SW2, configure interfaces GigabitEthernet0/1 and 0/2 with speed 1000, duplex full, and on the port-channel interface, set allowed VLANs to 10,20.
Why it's wrong here
This is incorrect because the allowed VLAN list on the port-channel interface is missing VLAN 30, which is required by the trunk configuration. The EtherChannel may form but will not pass traffic for VLAN 30.
- ✗
On SW2, configure interfaces GigabitEthernet0/1 and 0/2 with speed 1000, duplex full, and on the port-channel interface, set allowed VLANs to 1-4094.
Why it's wrong here
This is incorrect because allowing all VLANs (1-4094) is not the same as explicitly allowing only VLANs 10, 20, and 30. The requirement specifies a restricted set, and using 'allowed vlan all' may introduce security or operational issues.
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.
✓On SW2, configure interfaces GigabitEthernet0/1 and 0/2 with speed 1000, duplex full, and on the port-channel interface, set allowed VLANs to 10,20,30.Correct answer▾
Why this is correct
Configuring both member interfaces with speed 1000 and duplex full matches SW1's negotiated physical parameters, which is mandatory for LACP to treat them as eligible for bundling into a single port-channel. Setting the allowed VLAN list to 10,20,30 on the port-channel interface ensures the aggregated trunk forwards exactly the required VLANs, consistent with SW1's configuration. This is the only configuration that satisfies both the physical-layer prerequisites and the logical trunking requirements, allowing the EtherChannel to form and carry the needed VLANs.
✗On SW2, configure interfaces GigabitEthernet0/1 and 0/2 with speed 100, duplex half, and on the port-channel interface, set allowed VLANs to 10,20,30.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that LACP requires all member interfaces to have identical speed and duplex settings; changing SW2 to 100/half does not match SW1's 1000/full.
Why candidates choose this
Candidates might think they need to make both sides consistent by lowering SW1's settings, but the correct approach is to match the higher-capability side.
✗On SW2, configure interfaces GigabitEthernet0/1 and 0/2 with speed 1000, duplex full, and on the port-channel interface, set allowed VLANs to 10,20.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the trunk must allow all required VLANs; omitting VLAN 30 violates the requirement.
Why candidates choose this
Candidates might focus only on the speed/duplex issue and forget to update the VLAN allowed list, especially if they assume the existing list is correct.
✗On SW2, configure interfaces GigabitEthernet0/1 and 0/2 with speed 1000, duplex full, and on the port-channel interface, set allowed VLANs to 1-4094.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the configuration does not match the requirement to allow only VLANs 10, 20, and 30; it allows all VLANs instead.
Why candidates choose this
Candidates might think 'allowed vlan all' is a quick fix that covers the required VLANs, but it is overly permissive and not what the question asks for.
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?”
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Key term
LACP
LACP is a protocol that automatically combines multiple physical network links into a single logical link to increase bandwidth and provide redundancy.
Key term
Link Aggregation Control Protocol
Link Aggregation Control Protocol (LACP) is a standard protocol that automatically bundles multiple physical network links into a single logical link to increase bandwidth and provide redundancy.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.