Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A switch port and a host NIC have a duplex mismatch. Which symptom is most likely?
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
Best answer
Increased late collisions and poor performance
Correct. Duplex mismatch commonly leads to collisions and poor performance.
B
Distractor review
Incorrect VLAN tagging on trunks
VLAN tagging is unrelated to duplex mismatch.
C
Distractor review
OSPF area mismatch errors
OSPF area mismatches are Layer 3 control-plane issues, not duplex symptoms.
D
Distractor review
A change in the subnet mask on the host
Duplex does not alter IP addressing parameters.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is selecting answers related to Layer 3 or VLAN issues, such as OSPF area mismatches or VLAN tagging errors, when diagnosing duplex mismatch problems. Candidates might incorrectly associate poor network performance with routing or VLAN misconfigurations, but duplex mismatches are physical layer problems causing collisions and frame errors. Misinterpreting symptoms can lead to wrong troubleshooting steps and incorrect exam answers. Understanding that duplex mismatches specifically cause late collisions and degraded throughput on half-duplex links helps avoid this trap.
Technical deep dive
How to think about this question
Duplex mismatch occurs when one device on a link operates in full-duplex mode while the other operates in half-duplex mode. Full-duplex allows simultaneous sending and receiving of data without collisions, whereas half-duplex requires devices to take turns transmitting, which can cause collisions if not properly synchronized. This mismatch leads to performance degradation because the half-duplex device detects collisions that the full-duplex device does not expect, resulting in late collisions and retransmissions. In Cisco networking environments, duplex settings can be configured manually or negotiated automatically via auto-negotiation protocols. When auto-negotiation fails or is disabled on one side, a duplex mismatch can occur. The half-duplex side will experience increased late collisions and frame errors, causing poor throughput and network performance. Troubleshooting involves verifying and aligning duplex settings on both the switch port and the host NIC to ensure consistent operation. The exam trap lies in confusing duplex mismatch symptoms with Layer 3 or VLAN-related issues. For example, OSPF area mismatches or VLAN tagging problems do not cause collisions or duplex-related errors. Practically, duplex mismatches manifest as physical/link layer issues affecting frame transmission reliability, so recognizing collision-related symptoms is key to diagnosing duplex mismatches in Cisco networks.
KKey Concepts to Remember
- A duplex mismatch occurs when one device operates in full-duplex mode and the other in half-duplex mode on the same link, causing communication errors.
- Half-duplex devices detect collisions and must retransmit frames, while full-duplex devices do not expect collisions, leading to late collisions in mismatched links.
- Cisco switches and hosts use auto-negotiation to set duplex modes; disabling or misconfiguring this can cause duplex mismatches.
- Duplex mismatches cause increased late collisions, frame errors, and degraded throughput, especially impacting half-duplex devices.
- Duplex mismatch symptoms are physical layer issues and do not affect Layer 3 protocols like OSPF or IP addressing parameters such as subnet masks.
- Correct duplex configuration requires matching duplex settings on both the switch port and host NIC to prevent collisions and performance problems.
- Exam questions may tempt candidates to confuse duplex mismatch symptoms with VLAN tagging errors or routing protocol mismatches, which are unrelated.
- Troubleshooting duplex mismatches involves checking interface statistics for collisions and verifying duplex settings rather than examining Layer 3 configurations.
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?
A duplex mismatch occurs when one device operates in full-duplex mode and the other in half-duplex mode on the same link, causing communication errors.
What is the correct answer to this question?
The correct answer is: Increased late collisions and poor performance — A duplex mismatch often causes collisions, frame errors, and degraded throughput, especially on the half-duplex side. It is a classic physical/link layer performance problem.
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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