- A
Set the VoIP phones to use a static IP address
Why wrong: Static IPs help with management but do not prioritize traffic; QoS requires marking or queuing mechanisms.
- B
Configure DSCP markings on the VoIP traffic
DSCP marks packets with a priority level (e.g., EF for voice), enabling network devices to treat them with higher priority than data traffic.
- C
Enable VLAN tagging on the switch ports
Why wrong: VLANs separate traffic logically but do not prioritize it; QoS markings are still needed within the VLAN.
- D
Use a crossover cable between the phone and switch
Why wrong: Crossover cables are for connecting similar devices without auto-MDIX; they do not affect traffic prioritization.
Question 58 of 1,020
Prioritizing Voice Traffic Using DSCP QoS Markings
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?
Quick Answer
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.
Answer choices
Why each option matters
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) markings allow VoIP traffic to be classified and prioritized at Layer 3, ensuring low latency and jitter for voice packets. By marking VoIP packets with a specific DSCP value (e.g., EF for expedited forwarding), routers and switches can apply QoS policies to give voice traffic priority over data traffic. This is the standard method for QoS in VoIP deployments.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
- ✓
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
Read the scenario before looking for a memorised answer.
- ✗
Enable VLAN tagging on the switch ports
- ✗
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: answer the scenario, not the keyword
A common misconception is that VLAN tagging alone provides QoS, but VLANs only segregate traffic; prioritization requires Layer 3 markings like DSCP or Layer 2 CoS values.
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
DSCP markings are part of the IP header's ToS byte, with VoIP typically using EF (DSCP 46) for RTP traffic and AF41 (DSCP 34) for signaling. In a real-world scenario, a misconfigured DSCP value (e.g., using default 0) can cause voice packets to be dropped during congestion, even if VLANs are correctly set up. QoS policies must be applied consistently across all network devices, including the switch and router, to honor the markings.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
What to study next
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Network Configuration Concepts — This question tests Network Configuration Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure DSCP markings on the VoIP traffic — DSCP (Differentiated Services Code Point) markings allow VoIP traffic to be classified and prioritized at Layer 3, ensuring low latency and jitter for voice packets. By marking VoIP packets with a specific DSCP value (e.g., EF for expedited forwarding), routers and switches can apply QoS policies to give voice traffic priority over data traffic. This is the standard method for QoS in VoIP deployments.
What should I do if I get this 220-1201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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