Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A network engineer is troubleshooting intermittent call drops on a VoIP deployment. The network uses separate VLANs for voice (VLAN 20) and data (VLAN 10). Switch ports connecting the IP phones are configured with the correct voice VLAN. Which of the following is the MOST likely cause to check NEXT?
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
Verify that QoS markings and queuing are configured on the switches and routers
QoS ensures voice traffic is prioritized over data. Without proper QoS on all network devices, voice packets can be dropped when the network is congested.
B
Distractor review
Check the DNS server for the phone's name resolution
DNS is used for call server registration, but intermittent call drops are more indicative of a Layer 2/3 quality issue rather than a name resolution issue.
C
Distractor review
Replace the patch cables from the phones to the switches
Physical cabling issues usually cause complete disconnection or errors, not intermittent call drops without any link flapping. QoS is a more likely culprit.
D
Distractor review
Increase the DHCP lease time for the phones
DHCP lease time affects IP address renewal, not the quality of voice traffic during a call. It would cause loss of connectivity if the lease expires.
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: Verify that QoS markings and queuing are configured on the switches and routers — VoIP traffic (RTP) is sensitive to jitter and latency. If QoS is not correctly configured on all switch uplinks and routers, voice packets can be dropped or delayed during congestion, causing call drops.
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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