Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
Users in a department report that the network is extremely slow. A technician checks the access switch and notices that a single port shows a high number of CRC errors and runts. The link LED is solid green. Which of the following is the most likely cause of the issue?
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
Duplex mismatch between the switch port and the connected device
Duplex mismatch causes collisions and errors because one device transmits while the other cannot receive properly, leading to CRC and runt frames.
B
Distractor review
Faulty network cable
A faulty cable can cause errors, but the solid link LED indicates a physical connection. Duplex mismatch is a more common cause of CRC errors when the link is up.
C
Distractor review
Broadcast storm
A broadcast storm would cause high broadcast traffic on many ports, not necessarily CRC errors on a single port.
D
Distractor review
VLAN misconfiguration
VLAN misconfiguration typically causes connectivity issues (cannot reach resources) but does not directly result in CRC errors or runts.
Common exam trap
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Technical deep dive
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
- Access ports place end devices into a single VLAN.
- Trunk ports carry multiple VLANs between switches.
- Allowed VLAN lists decide which VLANs can cross a trunk.
- Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
- Use show vlan brief to verify access VLANs.
- Use show interfaces trunk to verify trunk state and allowed VLANs.
- Do not treat every same-VLAN issue as a routing problem.
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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 network engineer needs to connect two switches located 400 meters apart. The cable run includes high electromagnetic interference from nearby machinery. The engineer decides to use fiber optic cabling. Which transceiver type and fiber combination should be used to ensure the link reaches 400 meters while remaining cost-effective?
Question 2
A network engineer is designing a new switched network and needs to ensure that broadcast traffic from one department does not reach another department's workstations. The engineer plans to use VLANs. Which of the following must be configured on the switches to isolate broadcast domains as intended?
Question 3
A security engineer is configuring a site-to-site VPN between two branch offices. The requirement is to encrypt all traffic between the two networks using IPsec. Which IPsec mode should be used to encrypt the entire IP packet including the original header?
Question 4
A network administrator is connecting two switches to increase bandwidth and provide redundancy. Which technology should be used to combine multiple physical links into a single logical link?
Question 5
A network administrator is experiencing issues where unauthorized devices are offering IP addresses to clients, causing connectivity problems. Which security feature should be enabled on switches to prevent this?
Question 6
A network administrator is troubleshooting a connectivity issue and suspects the problem is related to the physical cabling. At which layer of the OSI model should the administrator begin their investigation?
FAQ
Questions learners often ask
What does this N10-009 question test?
Access ports place end devices into a single VLAN.
What is the correct answer to this question?
The correct answer is: Duplex mismatch between the switch port and the connected device — CRC errors and runts often indicate a physical layer problem, commonly a duplex mismatch. When one side is set to full duplex and the other to half duplex, collisions occur, leading to frame errors. A faulty cable could also cause errors, but the solid link LED suggests the cable is physically connected. A broadcast storm would affect all ports, not just one. A VLAN mismatch would not cause CRC errors.
What should I do if I get this N10-009 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
Discussion
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