Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
Exhibit
SW1: interface range g1/0/1-2 channel-group 1 mode active SW2: interface range g1/0/1-2 channel-group 1 mode on
Exhibit: SW1 is configured for EtherChannel with LACP, but the bundle does not form. What is the most likely cause?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
The interfaces should use PAgP instead of LACP on both ends
PAgP is not required; LACP works when both sides actually use it.
B
Best answer
One side is using LACP and the other side is using a static EtherChannel mode
Mode active expects LACP, while mode on does not negotiate.
C
Distractor review
The links must be routed ports before EtherChannel can form
Layer 2 EtherChannels are common and do not require routed ports.
D
Distractor review
EtherChannel requires three or more member links
Two links are enough.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is assuming that LACP can form an EtherChannel with a static mode (mode on) configuration on the other side. Because static mode does not negotiate, it cannot interoperate with LACP, which requires negotiation. This leads to the bundle not forming, even though the physical links are connected. Candidates might incorrectly select options suggesting PAgP or static mode alone can fix the issue, but the key is protocol and mode compatibility. Misunderstanding the difference between dynamic negotiation protocols and static configuration causes this frequent mistake.
Technical deep dive
How to think about this question
EtherChannel is a technology that aggregates multiple physical Ethernet links into a single logical link to increase bandwidth and provide redundancy. Cisco supports EtherChannel using protocols like LACP (Link Aggregation Control Protocol) and PAgP (Port Aggregation Protocol), or by configuring static EtherChannel mode (mode on). LACP is an IEEE standard protocol that dynamically negotiates link aggregation between switches, requiring both ends to participate in the negotiation process using active or passive modes. This negotiation ensures that only compatible links are bundled, preventing misconfigurations and loops. For an EtherChannel to form using LACP, both switches must be configured to use LACP modes that allow negotiation: active (actively initiates negotiation) or passive (responds to negotiation). If one side uses LACP and the other side is set to static mode (mode on), which does not negotiate, the bundle will fail to form because the static side does not send or respond to LACP packets. This mismatch is a common cause of EtherChannel failures in Cisco environments and is critical to understand for the CCNA exam. Both sides must use compatible modes and protocols for the EtherChannel to establish successfully. A frequent exam trap is confusing static EtherChannel mode with LACP or PAgP modes. Static mode forces the interface to bundle without negotiation, so if the other side expects LACP negotiation, the EtherChannel will not form. Practically, this means network engineers must verify that both ends use the same protocol and compatible modes to avoid link failures. Understanding this behavior helps troubleshoot EtherChannel issues and ensures reliable link aggregation in Cisco networks.
KKey Concepts to Remember
- EtherChannel bundles multiple physical links into a single logical link to increase bandwidth and provide redundancy between switches.
- LACP (Link Aggregation Control Protocol) requires both ends of the EtherChannel to negotiate using active or passive mode for the bundle to form.
- Static EtherChannel mode (mode on) does not perform negotiation and expects the other side to be configured identically to form a bundle.
- A mismatch between LACP-enabled ports and static mode ports prevents EtherChannel formation because the protocols do not interoperate.
- EtherChannel can be configured using either LACP, PAgP, or static mode, but both ends must use the same protocol and compatible modes.
- Two physical links are sufficient to form an EtherChannel; there is no requirement for three or more links.
- EtherChannel operates at Layer 2 or Layer 3, and does not require interfaces to be routed ports to form a bundle.
- LACP uses protocol negotiation to dynamically detect and aggregate links, improving link management and fault tolerance.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
EtherChannel bundles multiple physical links into a single logical link to increase bandwidth and provide redundancy between switches.
What is the correct answer to this question?
The correct answer is: One side is using LACP and the other side is using a static EtherChannel mode — For an LACP EtherChannel to form, both sides must negotiate with LACP using active or passive mode. One side here is set to channel-group mode on, which creates a static channel and does not speak LACP. That mismatch prevents the bundle from forming.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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