CCNA Switching and Network Access Practice Question
Which two conditions must match on two switch ports before they can successfully form a Layer 2 EtherChannel? (Choose two.)
⚠ Common exam trap
Remember that EtherChannel requires consistent speed and duplex settings, and also consistent switchport mode (access or trunk) and allowed VLANs.
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 switchport mode and VLAN settings
Layer 2 EtherChannel members must have compatible Layer 2 configuration. Port mode, VLAN-related settings, speed, and duplex all need to align for the bundle to form correctly.
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 switchport mode and VLAN settings
Why this is correct
For an EtherChannel to operate correctly, each member port on both switches must be assigned the same switchport mode (access or trunk) and, if trunking, the identical set of allowed VLANs. When mode or VLAN permissions differ across links, frames may be dropped or forwarded inconsistently because the channel treats all member ports as a single logical link, and STP or negotiation protocols will reject the bundle if these attributes disagree.
- ✗
The STP root bridge ID on both switches
Why it's wrong here
The STP root bridge ID is a per-switch global parameter selected by the spanning-tree algorithm, not a per-interface attribute. It does not have to match between the two switches in an EtherChannel, because STP treats the entire channel as a single logical bridge port and the root ID is used to elect the root switch, not to validate port compatibility.
When this WOULD be correct
In a different question asking about the prerequisites for a stable spanning tree topology, the STP root bridge ID would be relevant. For example, if the question focused on ensuring consistent spanning tree behavior across multiple switches, matching root bridge IDs would be necessary.
- ✓
The speed and duplex settings
Why this is correct
Each physical link in an EtherChannel must run at the same speed and duplex mode, because the channel's load-balancing algorithm expects symmetric link characteristics. A mismatch causes CRC errors, late collisions, or even physical link flaps, and when using Port Aggregation Protocol (PAgP) or Link Aggregation Control Protocol (LACP), the negotiation will fail if the auto-negotiation results differ on any port.
- ✗
The interface description
Why it's wrong here
An interface description is only a local administrative text field used for documentation or operational convenience; it is never transmitted to the peer switch. Since EtherChannel negotiation relies on exchanging protocol frames and checking physical and VLAN parameters, the description has no bearing on whether ports will join the channel.
When this WOULD be correct
In a question focused on network documentation or management best practices, where candidates are asked to identify the importance of consistent interface descriptions across switch ports for ease of troubleshooting and management, this option would be correct.
- ✗
The ARP timeout value
Why it's wrong here
The ARP timeout controls how long a device caches IP-to-MAC address mappings in its Layer 3 table, which is entirely unrelated to Layer 2 port aggregation. EtherChannel operates at the data link layer for link bonding and load sharing, so ARP timer settings on the switches do not need to be synchronized for the channel to form or function properly.
When this WOULD be correct
In a question focused on Layer 3 configurations or network performance optimization, a scenario might ask about factors that influence ARP behavior, where candidates must identify the correct ARP timeout settings for different network segments.
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 switchport mode and VLAN settingsCorrect answer▾
Why this is correct
For an EtherChannel to operate correctly, each member port on both switches must be assigned the same switchport mode (access or trunk) and, if trunking, the identical set of allowed VLANs. When mode or VLAN permissions differ across links, frames may be dropped or forwarded inconsistently because the channel treats all member ports as a single logical link, and STP or negotiation protocols will reject the bundle if these attributes disagree.
✗The STP root bridge ID on both switchesWrong answer — click to see why▾
Why this is wrong here
This option is wrong because the STP root bridge ID does not directly affect the formation of an EtherChannel; EtherChannel requires matching port configurations, not spanning tree parameters.
★ When this WOULD be the correct answer
In a different question asking about the prerequisites for a stable spanning tree topology, the STP root bridge ID would be relevant. For example, if the question focused on ensuring consistent spanning tree behavior across multiple switches, matching root bridge IDs would be necessary.
Why candidates choose this
Candidates may find this option tempting because they understand that STP is crucial for Layer 2 networks and might mistakenly believe that its parameters are relevant to EtherChannel formation.
✗The interface descriptionWrong answer — click to see why▾
Why this is wrong here
The interface description does not affect the formation of an EtherChannel, as it is merely a label for identification purposes and does not influence Layer 2 connectivity or protocol negotiation.
★ When this WOULD be the correct answer
In a question focused on network documentation or management best practices, where candidates are asked to identify the importance of consistent interface descriptions across switch ports for ease of troubleshooting and management, this option would be correct.
Why candidates choose this
Candidates may mistakenly believe that interface descriptions play a role in EtherChannel formation due to their importance in network documentation and clarity, leading to confusion about their technical relevance in this specific context.
✗The ARP timeout valueWrong answer — click to see why▾
Why this is wrong here
The ARP timeout value does not affect the formation of a Layer 2 EtherChannel, as EtherChannel operates at Layer 2 and is concerned with port configurations, not Layer 3 settings like ARP.
★ When this WOULD be the correct answer
In a question focused on Layer 3 configurations or network performance optimization, a scenario might ask about factors that influence ARP behavior, where candidates must identify the correct ARP timeout settings for different network segments.
Why candidates choose this
Candidates may confuse Layer 2 EtherChannel requirements with Layer 3 functionalities, mistakenly thinking that ARP settings could impact 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
Go deeper
Related to this question
Learn chapter
Configuring Switch Ports for Desktops, VoIP Phones, APs, IoT, and Virtualized Hosts
Key term
EtherChannel
EtherChannel is a technology that bundles multiple physical Ethernet links into a single logical link to increase bandwidth and provide redundancy.
Key term
VLAN
A VLAN logically segments a physical network into isolated broadcast domains without requiring separate physical switches.
About these practice questions
One of 1,389 original 200-301 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
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.