Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
Exhibit
SW1# show etherchannel summary Group Port-channel Protocol Ports 1 Po1(SD) LACP Gi1/0/1(I) Gi1/0/2(I) SW1 interface range gi1/0/1-2 channel-group 1 mode active SW2 interface range gi1/0/1-2 channel-group 1 mode on
Exhibit: SW1 and SW2 should form an EtherChannel, but the bundle does not come up. 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 switch priority values are mismatched
Priority can affect STP, not whether LACP negotiates with mode on.
B
Best answer
One side is using LACP active while the other side is set to on
Mode on does not negotiate LACP.
C
Distractor review
The native VLAN must be VLAN 1 for EtherChannel to form
That is not a requirement.
D
Distractor review
Gi1/0/2 cannot be bundled because interfaces must be in different VLANs
Bundled links must be configured consistently, not differently.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is selecting an answer related to VLAN or switch priority mismatches as the cause of EtherChannel failure. While VLAN consistency and STP priority affect network behavior, they do not prevent EtherChannel negotiation. The real trap is misunderstanding that 'mode on' disables negotiation, so it cannot form an EtherChannel with a side set to LACP active. This mismatch causes the bundle to stay down, which is a subtle but critical detail often overlooked under exam pressure.
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 and PAgP, or by forcing the channel with the 'mode on' setting. LACP uses negotiation modes—active and passive—to dynamically detect and form EtherChannel bundles. Active mode actively initiates negotiation, while passive mode only responds to negotiation requests. The 'mode on' setting disables negotiation and forces the link to bundle without protocol exchange. For EtherChannel to form successfully, both ends must agree on key parameters including speed, duplex, allowed VLANs, and most importantly, the channel mode. If one side is set to LACP active and the other side is set to 'mode on', the side using 'on' does not participate in LACP negotiation. This mismatch causes the LACP side to wait for negotiation responses that never arrive, preventing the EtherChannel bundle from coming up. Both sides must either use compatible LACP modes (active/passive) or both be set to 'on' to force the bundle. A common exam trap is confusing the 'mode on' setting with LACP active or passive modes. Candidates may incorrectly assume that 'mode on' will negotiate with LACP active, but it does not. This leads to EtherChannel failure and a down port-channel interface. In practical networks, mismatched channel modes cause troubleshooting challenges, as the physical links appear connected but the logical bundle never forms, impacting redundancy and bandwidth aggregation benefits.
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) uses negotiation modes such as active and passive to dynamically form EtherChannel bundles.
- The 'mode on' setting forces EtherChannel without negotiation, requiring both sides to be set to 'on' for the bundle to come up.
- Both ends of an EtherChannel must have matching channel modes; mismatched modes like 'active' and 'on' prevent successful negotiation.
- EtherChannel requires consistent configuration of speed, duplex, allowed VLANs, and channel protocol on all member interfaces.
- Native VLAN mismatches do not prevent EtherChannel formation but can cause VLAN tagging issues and traffic problems.
- Switch priority values affect Spanning Tree Protocol (STP) roles but do not impact EtherChannel negotiation or formation.
- Interfaces bundled in EtherChannel must have consistent VLAN membership; interfaces in different VLANs cannot be bundled together.
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 active while the other side is set to on — Both sides of an EtherChannel must agree on key parameters such as speed, duplex, allowed VLANs, and channel mode behavior. Here one side uses active and the other uses on, so LACP negotiation never happens and the port-channel stays down.
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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