mediumMultiple Choice
350-401 Practice Question: Examine the following configuration: policy-map…
Examine the following configuration:
policy-map MARKING
class VOICE
set dscp ef
class VIDEO
set dscp af41
class class-default
set dscp default
interface GigabitEthernet0/0
service-policy input MARKING
Which statement is true?
⚠ Common exam trap
Candidates often confuse marking with congestion management, assuming that QoS actions like 'set dscp' only take effect during congestion, when in fact marking is a non-congestion-dependent action that applies to every matching packet.
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
✓
Incoming packets matching the VOICE class will have their DSCP set to EF (46), VIDEO to AF41 (34), and all others to default (0).
The configuration applies the MARKING policy-map as a service-policy input on GigabitEthernet0/0. This means all incoming packets are classified and have their DSCP values set according to the policy: VOICE class packets get DSCP EF (46), VIDEO class packets get DSCP AF41 (34), and all other packets (class-default) get DSCP default (0). The 'set dscp' action is valid in the input direction and does not require congestion to take effect.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Incoming packets matching the VOICE class will have their DSCP set to EF (46), VIDEO to AF41 (34), and all others to default (0).
Why this is correct
In a Modular QoS CLI policy-map, the 'set dscp' action unconditionally rewrites the DSCP field of every packet that matches the class. Because the policy-map is attached with 'service-policy input', this marking occurs as packets enter the interface: voice traffic is set to EF (46), video to AF41 (34), and class-default traffic to 0. This makes the statement correct.
- ✗
The policy-map will only mark packets if the interface is congested.
Why it's wrong here
Marking actions in a policy-map execute on every matching packet regardless of interface congestion; congestion-based behavior is applied by queuing tools such as bandwidth, priority, and random-detect. The 'set dscp' command does not interact with queue thresholds or drop probabilities. Therefore, the claim that it only marks during congestion is false.
- ✗
The configuration is invalid because 'set dscp' cannot be used in a 'service-policy input' direction.
Why it's wrong here
The 'set dscp' command is standard in an ingress policy-map; marking at the edge is a common design to establish a trust boundary and allow downstream devices to classify traffic by the marked value. Cisco IOS does not restrict 'set dscp' to a particular direction—it is valid for both 'service-policy input' and 'service-policy output'. Thus the configuration is not invalid for this reason.
- ✗
The policy-map will remark the DSCP of outgoing packets on GigabitEthernet0/0.
Why it's wrong here
The policy-map is attached as a 'service-policy input' on GigabitEthernet0/0, meaning it inspects frames as they are received, not as they are transmitted. It therefore cannot remark the DSCP of outgoing packets on that interface; outbound remarking would require a policy-map with 'service-policy output'. The statement incorrectly reverses the policy direction.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 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 350-401 exam.