Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A user's computer is unable to obtain a DHCP lease after connecting to a new switch port. The user's computer displays an IP address in the 169.254.x.x range. Other users on the same VLAN can obtain IP addresses successfully. The switch port is configured for 802.1X authentication. 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 DHCP server has exhausted its address pool.
If the DHCP server were out of addresses, other users on the same VLAN would also fail to obtain leases. This is inconsistent with the scenario.
B
Distractor review
The switch port is in a blocked state due to a spanning tree loop.
A spanning tree loop would affect all devices on that port, not just DHCP, and would likely cause intermittent connectivity. Also, the port should transition to forwarding after convergence.
C
Best answer
The user's computer has not authenticated via 802.1X and is placed in a restricted VLAN.
With 802.1X, unauthenticated devices are often placed in a restricted VLAN that may not include the DHCP server or have limited access. This explains why the computer gets an APIPA address while other devices on the same physical port (if authenticated) work normally.
D
Distractor review
The network cable is faulty.
If the cable were faulty, the link would likely be down or have excessive errors. The computer obtained a link and attempted DHCP, so a cable fault is improbable.
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: The user's computer has not authenticated via 802.1X and is placed in a restricted VLAN. — The 169.254.x.x address indicates that the computer failed to obtain a DHCP lease. Since other users on the same VLAN can get IP addresses, the issue is specific to this switch port. 802.1X authentication places unauthenticated devices into a restricted (guest) VLAN that may not have a DHCP server or proper network access. The computer likely has not authenticated yet.
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.
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