The answer is that the network is not prioritizing VoIP traffic via QoS. When jitter and packet loss are present alongside intermittent call drops, the root cause is almost always a failure to configure Quality of Service, which ensures real-time voice packets are given priority over less time-sensitive data like web browsing or file downloads. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of how network services impact real-time applications; a common trap is to blame SIP, DHCP, or DNS, but those protocols handle signaling or addressing, not traffic prioritization. Remember that SIP sets up the call, but QoS keeps the call clear—a useful mnemonic is “SIP starts it, QoS smooths it.”
220-1201 Network Services Practice Question
This 220-1201 practice question tests your understanding of network services. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 company uses a cloud-based VoIP service, and users report intermittent call drops and poor audio quality. Network monitoring shows high jitter and packet loss. Which service is most likely contributing to the problem?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The network is not prioritizing VoIP traffic via QoS.
This question tests understanding of network services affecting real-time traffic. SIP is the signaling protocol for VoIP, but jitter and packet loss are typically caused by network congestion or QoS misconfiguration. DHCP, DNS, or RADIUS don't directly cause these symptoms.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The DHCP server is leasing IP addresses with a short lease time.
Why it's wrong here
Short lease times cause renewal traffic but not jitter or packet loss.
✗
The DNS server is responding slowly to queries.
Why it's wrong here
Slow DNS might delay call setup but doesn't cause jitter or packet loss during a call.
✗
The SIP server is overloaded with registration requests.
Why it's wrong here
SIP server overload can cause registration failures but not jitter or packet loss on established calls.
✓
The network is not prioritizing VoIP traffic via QoS.
Why this is correct
Without QoS, real-time traffic like VoIP competes with other data, causing jitter and packet loss.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Authentication checks who the user is.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Real-world example
How this comes up in practice
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
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 Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related 220-1201 questions on access control and AAA configuration.
Network Services — This question tests Network Services — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: The network is not prioritizing VoIP traffic via QoS. — This question tests understanding of network services affecting real-time traffic. SIP is the signaling protocol for VoIP, but jitter and packet loss are typically caused by network congestion or QoS misconfiguration. DHCP, DNS, or RADIUS don't directly cause these symptoms.
What should I do if I get this 220-1201 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related 220-1201 questions on access control and AAA configuration.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Authentication checks who the user is.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A customer complains that their VoIP phone intermittently drops calls. A technician checks the network and finds high latency and jitter during peak hours. Which network service should be configured to prioritize VoIP traffic?
medium
A.DHCP
✓ B.QoS
C.DNS
D.VPN
Why B: Quality of Service (QoS) is used to prioritize time-sensitive traffic like VoIP, reducing latency and jitter during congestion. DHCP assigns IPs, DNS resolves names, and VPN encrypts traffic but none prioritize packets. QoS markings (e.g., DSCP) ensure voice packets are handled first.
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Question Discussion
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