The correct answer is to configure DSCP markings on the VoIP traffic. DSCP, or Differentiated Services Code Point, is a Layer 3 QoS method that marks each packet’s header with a priority value, enabling routers and switches to treat voice traffic with higher precedence over standard data. This prioritization is essential for VoIP because it directly reduces latency and jitter, ensuring clear, real-time communication. On the CompTIA A+ Core 1 220-1201 exam, this concept tests your understanding of network QoS configurations, often appearing in scenario-based questions where a technician must choose between Layer 2 (like 802.1p) and Layer 3 marking. A common trap is selecting “port prioritization” or “traffic shaping,” which are less precise for end-to-end voice quality. Remember the memory tip: “DSCP for deep control” — it works across multiple network hops, unlike simpler switch-level methods.
220-1201 Network Configuration Concepts Practice Question
This 220-1201 practice question tests your understanding of network configuration concepts. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A technician is setting up a new VoIP phone system. To ensure voice quality, they need to prioritize voice traffic over data traffic on the network. Which QoS configuration method should be implemented?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure DSCP markings on the VoIP traffic
DSCP (Differentiated Services Code Point) is a Layer 3 QoS method that marks packets with priority values, allowing routers and switches to prioritize voice traffic. It is commonly used for VoIP to ensure low latency and jitter.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Set the VoIP phones to use a static IP address
Why it's wrong here
Static IPs help with management but do not prioritize traffic; QoS requires marking or queuing mechanisms.
✓
Configure DSCP markings on the VoIP traffic
Why this is correct
DSCP marks packets with a priority level (e.g., EF for voice), enabling network devices to treat them with higher priority than data traffic.
Related concept
Access ports place end devices into a single VLAN.
✗
Enable VLAN tagging on the switch ports
Why it's wrong here
VLANs separate traffic logically but do not prioritize it; QoS markings are still needed within the VLAN.
✗
Use a crossover cable between the phone and switch
Why it's wrong here
Crossover cables are for connecting similar devices without auto-MDIX; they do not affect traffic prioritization.
Common exam traps
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.
Trap categories for this question
Similar concept trap
Crossover cables are for connecting similar devices without auto-MDIX; they do not affect traffic prioritization.
Detailed technical explanation
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.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 220-1201 question in full detail.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 220-1201 questions on switching, trunking, and access-port configuration.
Network Configuration Concepts — This question tests Network Configuration Concepts — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: Configure DSCP markings on the VoIP traffic — DSCP (Differentiated Services Code Point) is a Layer 3 QoS method that marks packets with priority values, allowing routers and switches to prioritize voice traffic. It is commonly used for VoIP to ensure low latency and jitter.
What should I do if I get this 220-1201 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 220-1201 questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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