The answer is that the switchport mode mismatch between GigabitEthernet0/1 (trunk) and GigabitEthernet0/2 (access) will prevent the EtherChannel from forming. EtherChannel requires strict consistency across all member interfaces, meaning every interface in the channel must share the same switchport mode—either all trunk or all access—along with matching VLAN and native VLAN settings. This configuration violates that rule because Gi0/1 is set to trunk while Gi0/2 is set to access, causing the Port Aggregation Protocol (PAgP) negotiation to fail and the channel to remain down. On the ENCOR 350-401 exam, this scenario tests your understanding of Layer 2 EtherChannel prerequisites, often appearing as a trap where candidates overlook interface-level mode mismatches while focusing on channel-group numbers or PAgP modes. A common memory tip is to remember the "three S's" for EtherChannel success: Same speed, Same duplex, and Same switchport mode.
350-401 EtherChannel Practice Question
This 350-401 practice question tests your understanding of etherchannel. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The switchport mode mismatch between Gi0/1 (trunk) and Gi0/2 (access) will prevent the EtherChannel from forming.
EtherChannel requires all member interfaces to have the same switchport mode (all trunk or all access). Here, Gi0/1 is configured as trunk, but Gi0/2 is configured as access. This mismatch will prevent the channel from forming.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both 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 channel-group mode desirable is incompatible with trunk ports.
The port-channel interface must also be configured as access to match Gi0/2.
Why it's wrong here
Incorrect. The port-channel should match the member ports; the mismatch is between the two members.
✓
The switchport mode mismatch between Gi0/1 (trunk) and Gi0/2 (access) will prevent the EtherChannel from forming.
Why this is correct
Correct. All member ports must have the same switchport mode.
Related concept
Access ports place end devices into a single VLAN.
✗
The EtherChannel will form but only Gi0/1 will be active.
Why it's wrong here
Incorrect. The channel will not form due to the mismatch.
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
→Use show vlan brief to verify access VLANs.
→Use show interfaces trunk to verify trunk state and allowed VLANs.
→Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both 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 350-401 question in full detail.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 350-401 questions on switching, trunking, and access-port configuration.
EtherChannel — This question tests EtherChannel — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: The switchport mode mismatch between Gi0/1 (trunk) and Gi0/2 (access) will prevent the EtherChannel from forming. — EtherChannel requires all member interfaces to have the same switchport mode (all trunk or all access). Here, Gi0/1 is configured as trunk, but Gi0/2 is configured as access. This mismatch will prevent the channel from forming.
What should I do if I get this 350-401 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 350-401 questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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