Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
Exhibit
SW1# interface GigabitEthernet0/1 switchport mode trunk channel-group 1 mode active ! interface GigabitEthernet0/2 switchport mode trunk channel-group 1 mode active SW2# interface GigabitEthernet0/1 switchport mode trunk channel-group 1 mode active ! interface GigabitEthernet0/2 switchport mode access channel-group 1 mode active
Based on the exhibit, what is the most likely reason the EtherChannel bundle is not forming?
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
LACP requires both sides to use passive mode only.
This is wrong because active mode is valid and not the issue shown.
B
Best answer
One of the member links has an inconsistent switchport mode.
This is correct because trunk/access mismatch prevents the bundle from forming correctly.
C
Distractor review
EtherChannel can be used only on routed interfaces.
This is wrong because EtherChannel is commonly used on switched interfaces.
D
Distractor review
The channel-group number must be different on each side.
This is wrong because the channel-group number identifies the local bundle and can be the same.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is to incorrectly believe that LACP requires both sides to be in passive mode or that the channel-group numbers must differ on each side. In reality, LACP requires at least one side to be active to initiate negotiation, and channel-group numbers identify local bundles and can be the same on both ends. Another tempting mistake is to think EtherChannel only works on routed interfaces, but it is primarily designed for switched interfaces. These misconceptions distract from the actual issue, which is often a mismatch in switchport mode between member links preventing the bundle from forming.
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. It relies on consistent configuration across all member interfaces, including speed, duplex, VLAN membership, and especially switchport mode. Switchport mode defines whether an interface operates as an access port (carrying traffic for a single VLAN) or a trunk port (carrying traffic for multiple VLANs). Mismatched modes cause the EtherChannel to fail because the logical link requires uniform Layer 2 behavior. When forming an EtherChannel using LACP, the protocol negotiates link aggregation parameters between switches. Both sides must have compatible configurations, including matching switchport modes. If one interface is set to trunk mode and another to access mode, the EtherChannel bundle will not form because the traffic handling differs fundamentally. The channel-group number is a local identifier and does not need to differ between switches, so it is not a cause of failure. Additionally, EtherChannel is primarily used on switched interfaces, not routed interfaces. A common exam trap is to assume that LACP mode settings or channel-group numbers cause the failure. While these are important, the most frequent real-world and exam scenario is a mismatch in switchport mode. This mismatch prevents the bundle from forming and causes the links to operate independently, which can lead to network loops or suboptimal traffic flow. Understanding this behavior helps troubleshoot EtherChannel issues effectively and aligns with Cisco’s best practices for link aggregation.
KKey Concepts to Remember
- EtherChannel requires all member interfaces to have consistent switchport modes, such as all being trunk or all being access ports, to form a valid bundle.
- LACP (Link Aggregation Control Protocol) can operate in active or passive mode, and at least one side must be active for negotiation to succeed.
- The channel-group number identifies the local EtherChannel bundle and can be the same on both ends without causing issues.
- EtherChannel is commonly used on Layer 2 switched interfaces to aggregate bandwidth and provide redundancy, not limited to routed interfaces.
- A mismatch in switchport mode between member links prevents EtherChannel from forming because the interfaces do not share the same Layer 2 characteristics.
- EtherChannel bundles require matching VLAN configurations and trunking settings on all member interfaces to ensure consistent traffic forwarding.
- Cisco switches verify interface parameters such as speed, duplex, and switchport mode before allowing interfaces to join an EtherChannel bundle.
- Inconsistent interface configurations cause EtherChannel negotiation to fail, resulting in individual links operating separately rather than as a single logical link.
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 requires all member interfaces to have consistent switchport modes, such as all being trunk or all being access ports, to form a valid bundle.
What is the correct answer to this question?
The correct answer is: One of the member links has an inconsistent switchport mode. — The most likely reason is that the member interfaces are not configured consistently. In practical terms, EtherChannel requires important interface characteristics to match across all member links. Here, one side is configured as a trunk while the other is configured as an access port, so the channel cannot build correctly even though LACP is enabled. This is a high-value CCNA troubleshooting pattern because it mirrors real switch configuration errors very closely.
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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