CCNA Switching and Network Access Practice Question
Exhibit
interface GigabitEthernet0/1 switchport mode trunk channel-group 1 mode active interface GigabitEthernet0/2 switchport mode access channel-group 1 mode active
A network engineer is configuring an EtherChannel between two switches. After applying the configuration, the port-channel fails to form. What is the most likely reason?
⚠ Common exam trap
Always verify interface configurations for consistency when troubleshooting EtherChannel issues.
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
✓
The member links use different switchport modes, so the channel cannot form correctly.
The port-channel is not forming because the two member interfaces are not configured consistently. In practical terms, EtherChannel requires important characteristics to align across candidate member links. Here, one interface is a trunk and the other is configured as an access port, so the channel cannot be built cleanly. This is a classic EtherChannel consistency problem. The protocol alone is not enough if the member-link settings disagree.
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 member links use different switchport modes, so the channel cannot form correctly.
Why this is correct
For an EtherChannel to form, all member interfaces must share an identical configuration, including speed, duplex, VLAN membership, and critically the switchport mode. If one interface is configured as an access port while another is set to trunk, the channel negotiation sees a mismatch in the allowed VLAN set and tagging behavior, preventing the bundle from coming up. This is a common cause of an EtherChannel failing to form even when LACP is enabled on both sides, because the compatibility checks are strict.
- ✗
LACP requires both interfaces to use different channel-group numbers.
Why it's wrong here
The correct requirement is the opposite: all member interfaces that are to join the same EtherChannel bundle must be assigned the identical channel-group number, as well as the same protocol (such as LACP active or passive). If LACP interfaces use different channel-group numbers, they would be treated as separate bundles or remain ungrouped, not as one logical channel. Therefore, a mismatch in channel-group numbers would itself cause the bundle to fail, making this option incorrect as an explanation for a formation issue.
When this WOULD be correct
In a different scenario, if a question asked about a misconfiguration where two interfaces were incorrectly assigned to different channel-group numbers while trying to form a port-channel, this option would be correct. The question would need to specify that the interfaces are intended to be aggregated but are configured incorrectly.
- ✗
The interfaces must both be configured for PPP.
Why it's wrong here
PPP is a WAN encapsulation protocol used on serial point-to-point links, not on Ethernet switch interfaces. EtherChannel operates by bundling Ethernet links at Layer 2, and the physical layer encapsulation must remain Ethernet. Configuring PPP on a switchport is not a valid or supported operation, and it would not affect the formation of an EtherChannel because the channel negotiates based on LACP or PAgP parameters, not on WAN encapsulations.
When this WOULD be correct
In a different scenario where the question specifies that the interfaces are intended to connect over a WAN link using PPP and are part of a port-channel, then this option could be correct. For instance, if the question states that both interfaces must support PPP for proper encapsulation, this would validate the claim.
- ✗
The bundle fails because BGP is not enabled on the switch.
Why it's wrong here
BGP is an exterior gateway protocol used to exchange routing information between autonomous systems at Layer 3. EtherChannel is a link aggregation technology that bundles multiple physical Ethernet links into one logical link, and it operates independently of any routing protocol. The channel formation relies on Link Aggregation Control Protocol (LACP) or Port Aggregation Protocol (PAgP) negotiation and link parameters, so BGP being disabled or enabled has no bearing on whether the port channel is established.
When this WOULD be correct
In a different question setup, if the context involved a scenario where BGP was explicitly required for establishing a specific type of connection or routing policy between switches, then this option could be correct. For example, if the question asked about the prerequisites for a BGP session over a port-channel, this option might apply.
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.
✓The member links use different switchport modes, so the channel cannot form correctly.Correct answer▾
Why this is correct
For an EtherChannel to form, all member interfaces must share an identical configuration, including speed, duplex, VLAN membership, and critically the switchport mode. If one interface is configured as an access port while another is set to trunk, the channel negotiation sees a mismatch in the allowed VLAN set and tagging behavior, preventing the bundle from coming up. This is a common cause of an EtherChannel failing to form even when LACP is enabled on both sides, because the compatibility checks are strict.
✗LACP requires both interfaces to use different channel-group numbers.Wrong answer — click to see why▾
Why this is wrong here
LACP requires that all member interfaces in the same port-channel use the same channel-group number. Using different numbers would place them in separate bundles, preventing the intended aggregation.
★ When this WOULD be the correct answer
In a different scenario, if a question asked about a misconfiguration where two interfaces were incorrectly assigned to different channel-group numbers while trying to form a port-channel, this option would be correct. The question would need to specify that the interfaces are intended to be aggregated but are configured incorrectly.
Why candidates choose this
Students may confuse the requirement for consistent channel-group numbers with the idea that different numbers are needed for load balancing or protocol operation, but in reality, all members of a single EtherChannel must share the same channel-group number.
✗The interfaces must both be configured for PPP.Wrong answer — click to see why▾
Why this is wrong here
PPP is a Layer 2 encapsulation used on serial links, not on Ethernet switch ports. EtherChannel on Cisco switches uses Ethernet frames, and PPP is irrelevant to the configuration of port-channels.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that the interfaces are intended to connect over a WAN link using PPP and are part of a port-channel, then this option could be correct. For instance, if the question states that both interfaces must support PPP for proper encapsulation, this would validate the claim.
Why candidates choose this
A student might associate PPP with link aggregation protocols like Multilink PPP (MLPPP) used on WAN interfaces, and incorrectly assume it applies to Ethernet EtherChannel.
✗The bundle fails because BGP is not enabled on the switch.Wrong answer — click to see why▾
Why this is wrong here
BGP is a routing protocol that operates at Layer 3 and is not required for EtherChannel formation. EtherChannel is a Layer 2 technology that bundles physical links into a single logical link, independent of any routing protocol.
★ When this WOULD be the correct answer
In a different question setup, if the context involved a scenario where BGP was explicitly required for establishing a specific type of connection or routing policy between switches, then this option could be correct. For example, if the question asked about the prerequisites for a BGP session over a port-channel, this option might apply.
Why candidates choose this
Students may think that because BGP is used in complex network designs, it might be a prerequisite for advanced features like EtherChannel, but BGP has no role in the link aggregation process.
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
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
Configuring Switch Ports for Desktops, VoIP Phones, APs, IoT, and Virtualized Hosts
Key term
Access port
An access port is a switch port that connects to a single end device, like a computer or printer, and carries traffic for only one VLAN.
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.