- A
Classification can be based on IP precedence, DSCP, or CoS values.
Correct because classification matches existing markings like IP precedence, DSCP, or CoS.
- B
Marking is performed using the 'set' command in a policy-map class configuration.
Correct because the 'set' command is used in Cisco IOS to mark packets with a new QoS value.
- C
Layer 2 CoS marking uses the first 6 bits of the 802.1Q tag.
Why wrong: Incorrect because CoS uses only the first 3 bits of the 802.1Q tag; the remaining bits are for CFI and VLAN ID.
- D
DSCP uses the first 3 bits of the ToS byte and is not compatible with IP precedence.
Why wrong: Incorrect because DSCP uses the first 6 bits of the ToS byte, and it is backward-compatible with IP precedence (which uses the first 3 bits).
- E
The 'match ip dscp' command can be used in a class map to match packets based on DSCP values.
Correct because 'match ip dscp' is a valid command in a class map to classify by DSCP.
Quick Answer
The answer is that the 'match ip dscp' command is used in a class map to match packets based on DSCP values, and classification identifies traffic while marking sets the QoS value. This is correct because classification and marking in MQC commands operate through a two-step process: class maps define the traffic to match using criteria like DSCP, IP precedence, or CoS, while policy maps apply the marking action. On the ENCOR 350-401 exam, this topic tests your ability to distinguish between Layer 2 and Layer 3 marking, with a common trap being confusion over DSCP’s 6-bit field versus IP precedence’s 3-bit field—remember that DSCP is backward-compatible with IP precedence but offers finer granularity. A useful memory tip is to think of DSCP as “Differentiated Services Code Point” using six bits for 64 classes, while IP precedence uses only three bits for eight classes, and CoS is strictly for Layer 2 Ethernet frames.
CCNP QoS Practice Question
This 350-401 practice question tests your understanding of qos. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Which two statements about classification and marking in QoS are true? (Choose two.)
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
Classification can be based on IP precedence, DSCP, or CoS values.
Classification identifies traffic, and marking sets the QoS value. MQC uses class maps and policy maps. Layer 2 marking uses CoS bits, while IP precedence uses the first 3 bits of the ToS byte. DSCP uses 6 bits and is backward-compatible with IP precedence.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Classification can be based on IP precedence, DSCP, or CoS values.
- ✓
Marking is performed using the 'set' command in a policy-map class configuration.
- ✗
Layer 2 CoS marking uses the first 6 bits of the 802.1Q tag.
- ✗
DSCP uses the first 3 bits of the ToS byte and is not compatible with IP precedence.
Why it's wrong here
Incorrect because DSCP uses the first 6 bits of the ToS byte, and it is backward-compatible with IP precedence (which uses the first 3 bits).
- ✓
The 'match ip dscp' command can be used in a class map to match packets based on DSCP values.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-401 NAT questions on configuration and troubleshooting.
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FAQ
Questions learners often ask
What does this 350-401 question test?
QoS — This question tests QoS — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Classification can be based on IP precedence, DSCP, or CoS values. — Classification identifies traffic, and marking sets the QoS value. MQC uses class maps and policy maps. Layer 2 marking uses CoS bits, while IP precedence uses the first 3 bits of the ToS byte. DSCP uses 6 bits and is backward-compatible with IP precedence.
What should I do if I get this 350-401 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-401 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 18, 2026
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