CCNA Network Services and Security Practice Question
Exhibit
SW1: interface range g1/0/1-2 channel-group 5 mode active SW2: interface range g1/0/1-2 channel-group 5 mode on
Two switches are configured to form an EtherChannel, but the bundle never comes up. Which explanation best describes this scenario?
⚠ Common exam trap
Ensure you match the correct protocol and mode on both sides of the link; mixing protocols or incompatible modes will prevent channel formation.
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
✓
LACP active on one side is incompatible with mode on on the other side.
One side is using LACP active mode and the other side is forcing a static channel-group with mode on. Those modes are not compatible. LACP needs active or passive on both sides, while PAgP uses desirable or auto, and static mode on expects a manual bundle on the other side.
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 switches are using different native VLANs.
Why it's wrong here
Although mismatched native VLANs on an 802.1Q trunk can cause spanning-tree loops or misclassified traffic, they do not affect the ability of the two switches to negotiate an EtherChannel. The EtherChannel control plane (LACP/PAgP or static on) runs independently of the trunk VLAN configuration, so the bundle can still come up and later carry frames with incorrect VLAN tagging.
When this WOULD be correct
In a different question, if the context involved troubleshooting a trunk link where the native VLANs on both switches were indeed mismatched, this option would be correct. For example, if the question specified that the EtherChannel was configured for trunking and the native VLANs were different, it could lead to a failure in establishing the trunk.
- ✓
LACP active on one side is incompatible with mode on on the other side.
Why this is correct
LACP active mode actively sends LACPDUs to negotiate the bundle, while 'mode on' forces the channel statically without sending any negotiation frames. Because the 'on' side never responds to LACP, the active side cannot establish a working partner and the EtherChannel fails to form. The mismatch is a fundamental protocol/config mode incompatibility, not a wiring or VLAN issue.
- ✗
Both sides must use PAgP desirable mode.
Why it's wrong here
PAgP is a Cisco proprietary aggregation protocol, but it is entirely optional; LACP and static 'on' mode are both valid alternatives that can form a channel. Requiring PAgP desirable on both sides would only apply to a PAgP-based negotiation, not to a scenario where LACP is already configured on one side. The problem is the mismatch between LACP and static on, not the absence of PAgP.
When this WOULD be correct
In a different scenario where the question specifies that both switches are configured to use PAgP, and one switch is set to 'desirable' mode while the other is set to 'auto', this option would be correct. The question would need to focus on PAgP specifically, rather than LACP.
- ✗
The interfaces must be configured as routed ports first.
Why it's wrong here
EtherChannel is a layer-2 aggregation feature by default; it bundles switchports that may be configured as access or trunk ports without any need for a routed interface. Routed ports are only required if the administrator specifically intends to create a Layer 3 EtherChannel with an IP address at the logical interface. Since the question does not imply a routed topology, the failure to form a bundle cannot be attributed to missing routed-port configuration.
When this WOULD be correct
In a different scenario where the question specifies that the switches are intended to connect as routed ports for Layer 3 communication, and the exam asks about the prerequisites for establishing an EtherChannel in that context, this option would be correct.
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.
✓LACP active on one side is incompatible with mode on on the other side.Correct answer▾
Why this is correct
LACP active mode actively sends LACPDUs to negotiate the bundle, while 'mode on' forces the channel statically without sending any negotiation frames. Because the 'on' side never responds to LACP, the active side cannot establish a working partner and the EtherChannel fails to form. The mismatch is a fundamental protocol/config mode incompatibility, not a wiring or VLAN issue.
✗The switches are using different native VLANs.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because different native VLANs do not prevent an EtherChannel from forming; they can still establish a link if other configurations are compatible. The primary issue in this scenario is related to LACP mode mismatches.
★ When this WOULD be the correct answer
In a different question, if the context involved troubleshooting a trunk link where the native VLANs on both switches were indeed mismatched, this option would be correct. For example, if the question specified that the EtherChannel was configured for trunking and the native VLANs were different, it could lead to a failure in establishing the trunk.
Why candidates choose this
Candidates may choose this option because they recall that native VLAN mismatches can cause issues in VLAN communication, leading them to mistakenly believe it would also affect EtherChannel formation.
✗Both sides must use PAgP desirable mode.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because EtherChannel can use either PAgP or LACP for negotiation, and both protocols can operate independently of each other. The requirement for both sides to use PAgP in desirable mode is not a necessity for EtherChannel to function.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that both switches are configured to use PAgP, and one switch is set to 'desirable' mode while the other is set to 'auto', this option would be correct. The question would need to focus on PAgP specifically, rather than LACP.
Why candidates choose this
Candidates may choose this option due to a common misconception that both ends of an EtherChannel must use the same protocol, leading them to believe that PAgP modes are strictly required for successful configuration.
✗The interfaces must be configured as routed ports first.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because EtherChannel can be configured on switch ports without needing to convert them to routed ports. Routed ports are not necessary for EtherChannel to function, as it operates at Layer 2.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that the switches are intended to connect as routed ports for Layer 3 communication, and the exam asks about the prerequisites for establishing an EtherChannel in that context, this option would be correct.
Why candidates choose this
Candidates may find this option tempting because they might confuse EtherChannel configurations with routed port requirements, leading them to believe that all interfaces must be Layer 3 before forming a channel.
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
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.
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.
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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.