Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A network administrator adds a new server to VLAN 20. The switch port is configured as an access port in VLAN 20, and the server has a correct static IP address in that subnet. However, the server cannot communicate with other devices in the same VLAN. The VLAN exists on the switch and other devices in VLAN 20 are working. What is the most likely cause of this 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
The switch port is configured as a trunk port instead of an access port
A trunk port expects 802.1Q tagged frames; the server sends untagged frames, so the switch may not associate them with VLAN 20, causing communication failure within the VLAN.
B
Distractor review
VLAN 20 is not allowed on the trunk to the router
This would affect communication to other VLANs, not within the same VLAN. Intra-VLAN communication does not go through the router.
C
Distractor review
The server does not have a default gateway configured
A default gateway is only required for communication outside the local subnet. It is not needed for devices in the same VLAN.
D
Distractor review
The port is administratively down
If the port were down, there would be no connectivity at all, but the question implies the server is connected (just unable to communicate).
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 switch port is configured as a trunk port instead of an access port — If the switch port is accidentally configured as a trunk port, it will expect tagged frames from the server. A standard access port sends and receives untagged frames. When the server sends untagged frames to a trunk port, the switch may not forward them correctly to other access ports in VLAN 20, breaking communication.
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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