Quick Answer
The answer is MQC with NBAR. NBAR, or Network-Based Application Recognition, performs deep packet inspection up to Layer 7, allowing the router to identify application-layer traffic like HTTP, DNS, or proprietary protocols by examining the payload itself. This capability is essential for QoS classification on a PE router when the goal is to differentiate customer traffic based on application type rather than just port numbers or IP addresses. On the Cisco SPCOR 350-501 exam, this question tests your understanding that NBAR operates within the Modular QoS CLI (MQC) framework, and a common trap is selecting simple ACLs or class maps based only on Layer 3/4 headers, which cannot see application-layer information. Remember that NBAR is the only tool that can look beyond the TCP/UDP header to match specific applications, making it the correct choice for this scenario. A helpful memory tip: NBAR sees the app, not just the port.
This 350-501 practice question tests your understanding of services. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 service provider is implementing QoS on a PE router for customer traffic. Which tool should be used to classify traffic based on application layer information?
Access-list
Why wrong: Incorrect. Access-lists classify based on IP addresses, ports, and protocols, not application layer.
MQC with NBAR
Correct. NBAR can classify traffic based on application signatures.
Shaping
Why wrong: Incorrect. Shaping is an action to smooth traffic rates, not classify.
Policy-map with police
Why wrong: Incorrect. Police is an action to enforce a rate, not a classification mechanism.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
MQC with NBAR
NBAR (Network-Based Application Recognition) is a deep packet inspection (DPI) engine within the Modular QoS CLI (MQC) that can identify applications by inspecting payloads up to Layer 7. This allows classification of traffic based on application-layer information such as HTTP, DNS, or proprietary protocols, which is exactly what the question requires.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Access-list
Why it's wrong here
Incorrect. Access-lists classify based on IP addresses, ports, and protocols, not application layer.
MQC with NBAR
Why this is correct
Correct. NBAR can classify traffic based on application signatures.
Related concept
Read the scenario before looking for a memorised answer.
Shaping
Why it's wrong here
Incorrect. Shaping is an action to smooth traffic rates, not classify.
Policy-map with police
Why it's wrong here
Incorrect. Police is an action to enforce a rate, not a classification mechanism.
Common exam traps
Cisco often tests the distinction between classification tools (NBAR, ACLs) and QoS actions (shaping, policing), so the trap here is that candidates confuse a QoS action (like shaping or policing) with the classification mechanism itself.
Detailed technical explanation
NBAR uses protocol discovery and a protocol pack (e.g., Protocol Pack 16.0) to recognize over 1,000 applications, including encrypted traffic via NBAR2’s application recognition engine. It can match on application groups, sub-applications, or custom signatures, and the classification is performed in the control plane before the QoS policy is applied in the data plane. In real-world deployments, NBAR is often combined with a policy-map to mark traffic (e.g., set dscp ef) after classification.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Services — study guide chapter
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FAQ
Services — This question tests Services — Read the scenario before looking for a memorised answer..
The correct answer is: MQC with NBAR — NBAR (Network-Based Application Recognition) is a deep packet inspection (DPI) engine within the Modular QoS CLI (MQC) that can identify applications by inspecting payloads up to Layer 7. This allows classification of traffic based on application-layer information such as HTTP, DNS, or proprietary protocols, which is exactly what the question requires.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This 350-501 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-501 exam.
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